WO2001031077A1 - Hot-dip galvanized steel sheet having high strength and also being excellent in formability and galvanizing property - Google Patents

Hot-dip galvanized steel sheet having high strength and also being excellent in formability and galvanizing property Download PDF

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Publication number
WO2001031077A1
WO2001031077A1 PCT/JP2000/007115 JP0007115W WO0131077A1 WO 2001031077 A1 WO2001031077 A1 WO 2001031077A1 JP 0007115 W JP0007115 W JP 0007115W WO 0131077 A1 WO0131077 A1 WO 0131077A1
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Prior art keywords
less
hot
steel sheet
rolled
dip galvanized
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PCT/JP2000/007115
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French (fr)
Japanese (ja)
Inventor
Kazunori Osawa
Kei Sakata
Osamu Furukimi
Yoshitsugu Suzuki
Akio Shinohara
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Kawasaki Steel Corporation
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Application filed by Kawasaki Steel Corporation filed Critical Kawasaki Steel Corporation
Priority to EP00966468A priority Critical patent/EP1146132B1/en
Priority to CA002353492A priority patent/CA2353492C/en
Priority to US09/868,674 priority patent/US6537394B1/en
Priority to DE60033498T priority patent/DE60033498T2/en
Priority to AU76857/00A priority patent/AU773014B2/en
Publication of WO2001031077A1 publication Critical patent/WO2001031077A1/en

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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0236—Cold rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/022—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by heating
    • C23C2/0224—Two or more thermal pretreatments
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/02—Pretreatment of the material to be coated, e.g. for coating on selected surface areas
    • C23C2/024—Pretreatment of the material to be coated, e.g. for coating on selected surface areas by cleaning or etching
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
    • C23C2/26—After-treatment
    • C23C2/28—Thermal after-treatment, e.g. treatment in oil bath
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0278—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular surface treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
    • C21D8/0478—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing involving a particular surface treatment

Definitions

  • the present invention relates to a method for producing a high-strength molten steel port and a plated steel sheet (including a high-strength alloyed hot-dip galvanized steel sheet) suitable for use as an inner plate and an outer plate of an automobile.
  • the desired strength and workability can be obtained after good plating properties and after passing through a hot-dip galvanizing bath or further alloying treatment.
  • a solid solution strengthening element such as Mn, Si and P and a precipitation strengthening element such as Ti, Nb and V are added. It is known that the plating properties deteriorate when a steel sheet added with a caulking element is treated at the continuous melting port and plating line (CGL). As described above, the content of the alloying element has a contradictory effect on the strength and the plating property, so that it is extremely difficult to produce a high-strength hot-dip galvanized steel sheet in a continuous hot-dip plating line with poor plating properties. It was something. In addition, high-strength hot-dip galvanized steel sheets generally have inferior properties related to workability such as elongation, so that it was even more difficult to produce hot-dip galvanized steel sheets with good workability.
  • a multi-structure steel sheet containing a low-temperature transformation phase (including retained austenite) mainly containing martensite in a ferrite base is known.
  • This composite structure steel sheet is non-ageed at room temperature, has a low yield ratio, and has excellent workability and bake hardenability after processing.After heating at the ferrite + austenite ( ⁇ + ⁇ ) two-phase region temperature, it can be cooled by water or gas. It is manufactured by quenching.
  • this composite structure steel sheet is hot-dip galvanized at a temperature of about 500 ° C or further alloyed, the martensite dispersed in the ferrite base material is tempered, and the tensile strength is increased. However, the elongation decreases, the upper yield point appears, the yield ratio increases, and the yield point elongation occurs.
  • Tempering softening is more likely to occur as the amount of alloying elements such as Mn and Si decreases, while when the amount of these alloying elements is high, the hot-dip galvanizing property decreases.
  • martensite is tempered in the plating process even in a composite structure steel sheet, and it is difficult to achieve both good workability and high strength, which are the characteristics of the martensite, and to exhibit good plating properties. It was difficult below.
  • PCT / JP99 / 04385 added Mo and Cr, which are very important for the production of a dual-phase composite-structured steel sheet having a low-temperature transformation phase with martensite as the main phase, on the ferrite matrix described above. It is an invention for the case.
  • Mo and Cr are very expensive elements, and have a steel composition that is too costly to produce a general-purpose and inexpensive plated steel sheet as the object of the present invention.
  • Mo is added to a material with a large amount of Mn to form a dual phase composite steel sheet more advantageously. Becomes thicker.
  • PCT / JP00 / 02547 shows that Mn: 1.0-3.0%, Si 0.3-: I. 8% added, very important residue to improve strength-elongation balance
  • This is a steel sheet with a composite structure containing an austenitic phase and a tempered martensite phase.
  • a combination of a primary heating / cooling step and a secondary heating / cooling step is essential.
  • it is necessary to quench at a stretch to a temperature below the Ms point at a cooling rate of 10 ° C / s or more after heating, which poses a problem in terms of operation.
  • one heating- At least one extra heating / cooling step must be performed before the CGL line, which should have completed the cooling step. Disclosure of the invention
  • An object of the present invention is to propose a method for producing a high-strength hot-dip galvanized steel sheet that satisfies both requirements and that provides good plating properties.
  • a specific object of the present invention is to obtain good plating while satisfying TS: 590 MPa or more, E1: 25% or more, and TSXE 1 value: 15000 MPa ⁇ % or more as indices indicating workability and high strength. Is to be done.
  • the present inventors have conducted intensive studies for the above-mentioned solution, and as a result, have found that the workability and the workability are improved without adding Mo and Cr and without including the residual austenite phase and the tempered martensite phase.
  • the present inventor has discovered a high-strength hot-dip galvanized steel sheet having excellent plating properties and a manufacturing method, and has completed the present invention.
  • the gist of the present invention is as follows.
  • Mn more than 1.5 to 3.0 wt%
  • P 0.10 wt% or less
  • N contains 0.010 wt ° / 0 or less
  • One or more selected from Ti, Nb and V are contained in a total of 0.010 to 1.0 wt%, and the balance consists of the composition of Fe and unavoidable impurities and the area ratio of the ferrite phase. Is 50 wt% or more, the average grain size of the ferrite phase is 10 m or less, and the thickness of the band-like structure composed of the second phase is TbT ⁇ 0.005 (where Tb is the band-like structure).
  • the slab having the steel composition described in the above (1) or (2) is hot-rolled and wound at 750 to 450 ° C, and then directly or further cold-rolled to obtain the obtained hot-rolled steel.
  • High-strength hot-dip galvanized steel sheet with excellent workability and hot-dipability characterized in that the hot-dip or cold-rolled sheet is heated to 750 ° C or more and the hot dipping is performed during cooling from this temperature. Manufacturing method.
  • a slab having the steel composition described in (1) or (2) above is hot-rolled and wound at 750 to 450 T, and then directly or further cold-rolled to obtain a hot-rolled sheet.
  • High strength with excellent workability and adhesion characterized by heating a cold-rolled sheet to 750 ° C or more, performing hot-dip galvanizing during cooling from this temperature, and then performing alloying treatment.
  • Manufacturing method for hot-dip galvanized steel sheet is characterized by heating a cold-rolled sheet to 750 ° C or more, performing hot-dip galvanizing during cooling from this temperature, and then performing alloying treatment.
  • the slab having the steel composition described in the above (1) or (2) was hot-rolled and wound at 750 to 450 ° C, and then cold-rolled as it was or obtained.
  • the hot or cold rolled sheet is heated to 750 ° C or higher and cooled, and then heated to 700 ° C or higher, and hot-dip zinc plating is performed during cooling from this temperature.
  • the slab having the steel composition described in the above (1) or (2) is hot-rolled to 750 to 450 ° C. And then cold-rolled as it is or further, and the obtained hot-rolled or cold-rolled sheet is once heated to 750 ° C or more, cooled, and then further heated to 700 ° C or more.
  • ferrite (Hb) is formed by a pinning effect of grain boundary movement of carbides such as TiC, NbC and VC.
  • Crystal grains can be refined to 10 / zm or less, and ⁇ grains or austenite (y) single phase, which forms and grows in ferrite + austenite ( ⁇ + ⁇ ) two phase region when heated The effect of suppressing the coarse gamma of ⁇ grains in the region.
  • FIG. 1 is a graph showing the effect of the heating temperature in the continuous hot-dip galvanizing line on tensile strength (T S), yield strength (Y S), elongation (E 1), and plating properties.
  • FIG. 2 is a graph showing the effects of the application of two winding temperatures and the presence or absence of heating on the tensile strength (TS), yield strength (YS), elongation (E 1), and adhesion.
  • TS tensile strength
  • YS yield strength
  • E 1 elongation
  • adhesion adhesion
  • the plating property was evaluated by observing the surface visually and according to the following criteria.
  • FIG. Figure 1 shows that when the winding temperature is 650 ° C and the heating temperature before plating is 750 ° C or more, it is possible to achieve T S: 590 MPa or more and E 1: 25% or more.
  • the CT equivalent treatment was changed from 400 ° C to 700 ° C with the same components as in Experiment 1; KJ? Using a 1.6 mm cold-rolled plate, holding at 750 ° C for 1 minute (first heating) After cooling to room temperature at a rate of Z s at 10 and pickling, keeping it at 750 ° C for 1 minute (second heating), cooling to 500 ° C at a rate of 10 ° C s, and adding molten zinc After plating and holding for 40 s, it was heated to 550 ° C. with lCTCZ s for alloying, and immediately cooled to room temperature at the rate of lt cz s. After that, temper rolling was performed at a rolling reduction of 1.0%.
  • the tensile properties and plating properties of the obtained hot-dip galvanized steel sheet were determined in the same manner as in Experiment 1. Was examined. As a result, when two heatings (first heating and second heating) were performed ( ⁇ in Fig. 2), as shown in Fig. 2, both the tensile properties and the plating properties were reduced by only one heating. It can be seen that the improvement can be made even more than in the experiment similar to Experiment 1 (the climb in Fig. 2).
  • C is one of the important basic components of steel.In the present invention, in particular, in the present invention, it precipitates carbides of Ti, Nb, and V and contributes to the increase in strength, as well as through the bainite and martensite phases formed at low temperatures. It is an element that contributes to improvement in strength.
  • the C content is less than 0.01 wt%, not only the above-mentioned precipitates but also the bainite phase and the martensite phase are hardly formed, while if it exceeds 0.20 wt%, the spot weldability deteriorates. To 0.01 to 0.20 wt%.
  • the preferred C content is 0.03 to 0.15 wt%.
  • Si is an element that improves workability such as elongation by reducing the amount of solid solution C in the ⁇ phase.However, if the Si content exceeds 1.0 wt%, spot weldability and Since it is damaged, the upper limit is set to 1.0 wt%. The preferred amount of Si is 0.5 wt% or less. Further, it is costly to keep the content below 0.005 wt%, so the lower limit is preferably set to 0.005 wt%.
  • Mn is one of the important components in the present invention, and is an element that suppresses transformation in a composite structure and stabilizes a liquid phase. However, the addition of 1.5 wt% or less has no effect. On the other hand, if it exceeds 3.0 wt%, the spot weldability and the plating property are significantly impaired. Therefore, Mn
  • the upper limit should be 0.10 wt%. It is desirable to keep the P content to 0.05% by weight or less. In addition, since it is costly to keep the content below 0.001 wt%, the lower limit is preferably set to 0.001 wt%.
  • the upper limit is set to 0.05 wt% or less. It is more preferable to control the content to 0.010 wt% or less. In addition, since it is costly to suppress the content to less than 0.0005% by weight, the lower limit is preferably set to 0.0005% by weight.
  • A1 0.1 wt% or less
  • A1 is an effective element as a deoxidizing agent at the steelmaking stage, and fixes N that causes aging deterioration as A1N.
  • the content exceeds 0.1 wt%, the production cost will increase, so the amount of A1 must be suppressed to 0.1 ( ⁇ % or less.
  • the preferable content is 0.005 wt% or less. If the content is less than 0.005% by weight, sufficient deoxidation cannot be achieved, so the lower limit is preferably set to 0.005% by weight.
  • N must be suppressed to less than 0.010% because it causes aging deterioration, increases the yield point (yield ratio), and causes yield elongation.
  • the preferred N content is 0.0005 wt% or less.
  • the lower limit is preferably set to 0.0005 wt%.
  • Ti, Nb and V form carbides and are effective elements for increasing the strength of steel.
  • One or more of them are added in a total amount of 0.01 to 1.0 wt%.
  • the above effects can be obtained by adding these elements in a total amount of 0.0 ⁇ % or more.However, adding more than 1.0 wt% causes disadvantages in cost and excessively large amounts of fine precipitates. And suppresses recovery and recrystallization after cold rolling and reduces ductility (elongation). Therefore, these elements have a total amount of 0.01-1.0 wt%, preferably Alternatively, it is added in the range of 0.010 to 0.20 wt%.
  • Cu and Ni are elements that form a second phase such as martensite and are useful for increasing the strength of steel, and are added as necessary.
  • the total amount exceeds 3.0 wt ° / 0 , it not only increases the cost but also lowers the yield point, which is disadvantageous when a high yield ratio is required. Therefore, the total content of Cu and Ni should be 3.0 t% or less.
  • the preferable content range is a total amount of 0.010 to 3.0 wt%.
  • Ca and REM are preferably added in an amount of 0.001% by weight or more in order to control the form of inclusions and sulfides and to improve hole expandability.
  • adding more than 0.1 ⁇ % in total would increase the cost.
  • it is preferable that the content of 3,1 to £ 1 is added in the range of 0.001 to 0.10%.
  • a preferable content range is a range of 0.002 to 0.05 wt% in total amount.
  • Ferrite phase 50 wt% or more in area ratio
  • the present invention is directed to a steel sheet for automobiles requiring high workability, and if the area ratio of the ferrite phase is less than 50%, it becomes difficult to secure necessary ductility and stretch flangeability.
  • ⁇ which requires even better ductility, is desirably a ferrite fraction of 75 wt% or more in area ratio.
  • Ferrite shall include not only so-called ferrite but also vanitic ferrite which does not include precipitation of carbide, and ferrite.
  • the ferrite phase was observed and evaluated by embedding it in a resin so that the cross section of the steel plate was the observation surface, adding an aqueous solution containing 1 g of sodium pyrosulfite per 100 ml of pure water and a picrin solution for 100 ml of ethanol.
  • the solution containing 4 g of acid ” was immersed in a solution mixed at a ratio of 1: 1 at room temperature for 120 seconds for etching to separate it into a ferrite phase (black area) and a second phase (white area).
  • the area ratio of ferrite was determined with an image analyzer of X1000. Average grain size of ferrite phase: 10 / m (0.01 min.) Or less
  • the ferrite grain size is set to 10 / im or less in order to make the second phase finer and improve hole expandability.
  • the average crystal grain size is the value calculated from the cross-sectional structure photograph by the quadrature method specified in ASTM and the nominal grain size similarly obtained by the cutting method (for example, Umemoto et al .: Heat treatment 24 (1984) 334 Yes), whichever is larger.
  • the type of phase 2 martensite, bainite, perlite, cementite, etc.
  • the band-like structure of steel with a large amount of C and Mn is mainly due to the fact that the concentrated layer of C and Mn agglomerated along the grain boundaries during the cooling stage of the slab is elongated during hot rolling or subsequent cold rolling. This is a second phase group that is arranged in rows and layers in the rolling direction and the sheet width direction.
  • the reason why the ratio Tb / T of the band-like average thickness Tb to the plate thickness T is 0.005 or less is that when the Mn content is large as in the present invention, C and C are contained in the structure of the hot-rolled sheet.
  • the band-shaped second phase structure mainly composed of Mri becomes thicker, and it becomes difficult to produce a high-strength steel sheet in which hard martensite is uniformly dispersed in a ferrite base. Therefore, in order to efficiently manufacture a high-strength steel sheet, it is necessary to disperse C and Mn concentrated in the band-like second phase, and the standard is the average thickness of the band-like structure. This is the ratio of Tb to plate thickness T, and good results can be obtained if TbZT ⁇ 0.005.
  • Thickness of band-like structure The observation method and evaluation method of Tb were as follows: embedded in resin so that the cross section of the steel plate became the observation surface, immersed in 3% nital solution at room temperature for 15 seconds, and etched. Using an image analyzer, 20 rows and 2 layers of the second layer tissue were measured, and the average thickness Tb was determined.
  • a steel slab having the above-described composition is hot-rolled in a conventional manner and wound at 750 to 450 ° C. If the winding temperature is less than 450 ° C, carbides such as TiC and bC are not easily generated, and the strength tends to be insufficient. Also, it is difficult to form an internal oxide layer directly under the surface of the steel sheet. This is because Mn concentration on the surface cannot be suppressed. On the other hand, if the coil is wound above 750 ° C, the scale thickness will increase and the pickling efficiency will deteriorate, and the tip, center, and rear ends of the coil in the longitudinal direction, and the edge in the coil width direction This is because the material variation between the central portions becomes large.
  • the preferred winding temperature is 700 to 550 ° C.
  • the hot-rolled sheet is descaled by pickling as necessary, and then hot-rolled, or after further cold rolling, heated and cooled to 750 ° C or more in a continuous hot-dip galvanizing line. Perform hot-dip galvanizing.
  • the Mn and the like concentrated in the band-like yarn Prior to plating, by heating to a temperature range of 750 ° C or more (preferably 750 to 900 ° C) and cooling, the Mn and the like concentrated in the band-like yarn are dispersed, and the efficiency is improved.
  • Formability of ferrite + martensite can be formed to improve workability. That is, when the Mn content is high as in the present invention, a band-like second phase structure is easily formed in the hot-rolled sheet, and the concentration of Mn and the like in the ⁇ phase is reduced, which is disadvantageous for forming a composite structure. Become.
  • the gamma phase will be reduced when it is kept at around 500 ° C during the plating process of the continuous galvanizing line or the alloying process. Since the enrichment amount of Mn and the like in the inside increases, it becomes possible to disperse the martensite phase in the ferrite base material suitably.
  • the second heating is performed at 700 ° C or more.
  • the second heating is inevitably performed in the continuous hot-dip galvanizing line. If the second heating temperature is less than 700 ° C, the surface of the steel sheet is not reduced in the continuous hot-dip galvanizing line, and plating defects are likely to occur.
  • This second heating temperature is preferably in the range of 750 to 800 ° C.
  • the pickling conditions are preferably about 30 to 70 ° C. and about 3 to 10 s in a 1 to 10% HCl aqueous solution.
  • the molten zinc plating is performed.
  • the alloying treatment may be performed after the molten zinc plating is performed.
  • a 300 mm thick continuous slab with the chemical composition shown in Table 1 was heated to 1200 ° C, rolled for 3 passes, and then rolled to a 2.5 mm thick hot rolled sheet with a 7-stand finishing mill. And wound it up. After pickling the hot-rolled sheet, leave the hot-rolled sheet as it is, or cold-roll the hot-rolled sheet further to a thickness of 1.2 mm.
  • the average cooling rate of the steel sheet from heating to plating was 10 ° C / s.
  • the basis weight was adjusted to 60 g / m2 by gas wiping. . Thereafter, the sample was heated to 490 ° C, held for 20 seconds, and then cooled at an average cooling rate of 20 ° C / s to 200 ° C or less.
  • yield strength (YS), tensile strength (TS), elongation at break ( E 1) and yield elongation (YE 1) were measured.
  • TSS Tensile load
  • CTS tensile load
  • TS at a level of 590 to 690 MPa
  • E1 has a tensile characteristic of 25 wt% or more
  • TSXE1 15,000 MPa it% 3 ⁇ 4
  • balance of TSXE1 was also good, and it was found that there were no particular problems with the plating properties, alloying treatment properties, and spot weldability.
  • a continuous production slab having a chemical composition shown in Table 3 and having a thickness of 300 mm was heated to 1200 ° C, and after 3 passes & rolling, a 7-stand finishing rolling mill was used to produce a 3.0 mm-thick rolled sheet. It was wound at the temperatures shown in Table 4. After pickling, hot rolled sheet or hot rolled sheet is further cold rolled to a thickness of 1.2 mm, hot rolled sheet or hot rolled sheet is further cold rolled to a 1.2 mm thickness, (1) Continuous First heating at annealing line, second pickling at pickling and continuous heating at continuous hot-dip galvanizing line, or (2) Heating at continuous hot-dip galvanizing line at first hot-dip galvanizing Was further alloyed. Table 4 shows these manufacturing conditions.
  • the obtained steel sheet is used as a material to improve mechanical properties, plating properties, spot weldability, etc. And investigated in the same way. The results are shown in Table 4.
  • the average cooling rate of the steel sheet from heating to plating was 10 ° C.
  • the basis weight was adjusted to 60 g / m2 by gas wiping. Thereafter, the sample was heated to 490 ° C, held for 20 seconds, and then cooled at an average cooling rate of 20 ° C / s to 200 ° C or less.
  • the invention examples have good TSXE1 balance and high strength, but have no problem in plating property, alloying treatment property, and spot weldability.
  • a continuous production slab with a chemical composition shown in Table 5 and having a thickness of 300 mm was heated to 1200 ° C, rolled for 3 passes, and then heat-treated to a thickness of 3.0 mm with a 7-stand finishing mill. It was wound as a roll at the temperatures shown in Table 6. After pickling, cold-rolled to a thickness of 1.2 mm, first heating in a continuous annealing line, plating in a second heating step in a single pickling-continuous hot-dip galvanizing line, and further alloying . Table 6 shows these manufacturing conditions.
  • the obtained steel sheet was used as a sample, and mechanical properties, plating properties, spot weldability, and the like were similarly examined. The results are shown in Table 6.
  • the average cooling rate of the steel sheet from heating to plating was 10 ° C.
  • the basis weight was adjusted to 60 g / m2 by gas wiping. Thereafter, the sample was heated to 490 ° C, held for 20 seconds, and then cooled at an average cooling rate of 20 ° C / s to 200 ° C or less.
  • the invention example has a good balance of TSXE 1 and high strength. And no problem with plating, alloying, and spot weldability.o Industrial applicability
  • TSXE 1 It is possible to provide high-strength hot-dip galvanized steel sheets (including high-strength alloyed hot-dip galvanized steel sheets) with good balance. Therefore, the present invention makes it possible to reduce the weight and fuel consumption of automobiles, which greatly contributes to the improvement of the global environment.

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Abstract

A hot-dip galvanized steel sheet having a high strength and being excellent in formability and galvanizing property, characterized in that the steel has a chemical composition: C: 0.01 to 0.20 wt %, Si: 1.0 wt % or less, Mn: more than 1.5 wt % and 3.0 wt % or less, P: 0.10 wt % or less, S: 0.05 wt % or less, Al: 0.10 wt % or less, N: 0.010 wt % or less, one or more elements selected from among Ti, Nb and V: 0.010 to 1.0 wt % in total, and the balance: Fe and inevitable impurities, and has a metal structure wherein an area percentage of a ferrite phase is 50 % or more, an average grain diameter in the ferrite phase is 10 νm or less and the thickness of a band-shaped structure comprised of a second phase satisfies the relationship: Tb/T ≤ 0.005 wherein Tb represents an average thickness of the band-shaped structure in the direction of thickness of the sheet; and a method for producing the steel sheet. The galvanized steel sheet can be produced by the use of a continuous hot-dip galvanizing apparatus or the like, and has good formability and a high strength and also good galvanizing property.

Description

明細書 加工性およびめつき性に優れた高強度溶融亜鈴めつき鋼板ならびに その製造方法 技術分野  Description High-strength molten dumbbell-plated steel sheet excellent in workability and plating property, and its manufacturing method
本発明は、 自動車の内板、 外板などとしての使途に好適な高強度溶融 »口、めっき鋼 板 （高強度合金化溶融亜鉛めつき鋼板を含む） の製造方法に関するものである。 背景技術  TECHNICAL FIELD The present invention relates to a method for producing a high-strength molten steel port and a plated steel sheet (including a high-strength alloyed hot-dip galvanized steel sheet) suitable for use as an inner plate and an outer plate of an automobile. Background art
近年、 自動車の安全性、 軽量化および低燃費化、 ひいては地球環境の改善の観点か ら、 自動車用の鋼板として、 高強度の溶融亜鉛めつき鋼板を適用する傾向が増してい る。  In recent years, there has been an increasing tendency to use high-strength hot-dip galvanized steel sheets as automotive steel sheets from the viewpoints of automobile safety, weight reduction and fuel efficiency, and, in turn, improvement of the global environment.
高強度溶融亜鉛めつき鋼板を製造するためには、 めっき性がよく、 かつ溶融亜鉛め つき浴を通過し、 あるいはさらに合金化処理が施された後で、 所望の強度と加工性が 得られる鋼板でなければならない。  In order to produce high-strength hot-dip galvanized steel sheet, the desired strength and workability can be obtained after good plating properties and after passing through a hot-dip galvanizing bath or further alloying treatment. Must be steel plate.
一般に、 鋼板の強度を増加させるには、 Mn、 Si、 Pなどの固溶強化元素や Ti、 Nb、 Vなどの析出強ィ匕元素を添加している。 カゝかる元素を添加した鋼板を連続溶融 »口、め つきライン （C G L) で処理すると、 めっき性が劣化することが知られている。 このように合金元素の含有量は、 強度とめっき性に相反する作用を及ぼすので、 連 続溶融 めっきラインにて、 めっき性がよレ、高強度溶融亜鉛めつき鋼板を製造する ことは極めて困難なものであった。 また、 高強度溶融亜鉛めつき鋼板は、 一般に、 伸 ぴなどの加工性に関わる特性が劣るため、 加工性のよい溶融亜鉛めつき鋼板を製造す ることは、 さらに困難なことであった。  Generally, in order to increase the strength of a steel sheet, a solid solution strengthening element such as Mn, Si and P and a precipitation strengthening element such as Ti, Nb and V are added. It is known that the plating properties deteriorate when a steel sheet added with a caulking element is treated at the continuous melting port and plating line (CGL). As described above, the content of the alloying element has a contradictory effect on the strength and the plating property, so that it is extremely difficult to produce a high-strength hot-dip galvanized steel sheet in a continuous hot-dip plating line with poor plating properties. It was something. In addition, high-strength hot-dip galvanized steel sheets generally have inferior properties related to workability such as elongation, so that it was even more difficult to produce hot-dip galvanized steel sheets with good workability.
ところで、 従来の加工性を高めた高強度鋼板としては、 フェライト素地にマルテン サイトを主相とする低温変態相 （残留オーステナイトも含む） を含む複合組織鋼板が 知られている。 この複合組織鋼板は常温非時効で降伏比が低く、 加工性および加工後 の焼付硬化性が優れており、 フェライト +オーステナイト （α + γ ) 2相域温度で加熱 後、 水冷やガス冷却などで急冷することにより製造される。 しかしながら、 この複合組織鋼板を、 500 °C程度の温度で溶融亜鉛めつき、 あるい はさらに合金化処理した場合に、 フェライト素地中に分散しているマルテンサイトが 焼もどしされて、 引張強さ、 伸びは低下し、 上降伏点が現れて降伏比の上昇、 さらに は降伏点伸びの発生が起こってしまう。 By the way, as a conventional high-strength steel sheet with improved workability, a multi-structure steel sheet containing a low-temperature transformation phase (including retained austenite) mainly containing martensite in a ferrite base is known. This composite structure steel sheet is non-ageed at room temperature, has a low yield ratio, and has excellent workability and bake hardenability after processing.After heating at the ferrite + austenite (α + γ) two-phase region temperature, it can be cooled by water or gas. It is manufactured by quenching. However, when this composite structure steel sheet is hot-dip galvanized at a temperature of about 500 ° C or further alloyed, the martensite dispersed in the ferrite base material is tempered, and the tensile strength is increased. However, the elongation decreases, the upper yield point appears, the yield ratio increases, and the yield point elongation occurs.
焼もどし軟化は、 Mn、 Siなどの合金元素が少ないほど生じやすく、 一方、 これら合 金元素が多い場合には、 溶融亜鉛めつき性が低下してしまう。 結局、 複合組織鋼板に おいても、 めっき工程でマルテンサイトが焼きもどしされるので、 その特徴である加 工性と高強度を両立させ、 かつ良好なめっき性を発揮させることは、 従来技術の下で は困難であった。  Tempering softening is more likely to occur as the amount of alloying elements such as Mn and Si decreases, while when the amount of these alloying elements is high, the hot-dip galvanizing property decreases. As a result, martensite is tempered in the plating process even in a composite structure steel sheet, and it is difficult to achieve both good workability and high strength, which are the characteristics of the martensite, and to exhibit good plating properties. It was difficult below.
そこで、 めっき性の良好な高強度鋼板およびその製造方法の発明として、 本出願人 は、 別途、 国際出願番号： PCT/JP99/04385号および PCT/JP00/02547号を出願してい る。  Therefore, as an invention of a high-strength steel sheet having good plating properties and a method of manufacturing the same, the present applicant separately filed international application numbers: PCT / JP99 / 04385 and PCT / JP00 / 02547.
PCT/JP99/04385号は、上述のフェライト素地にマルテンサイトを主相とする低温変 態相を有する Dual Phase型の複合組織めつき鋼板を製造するのに非常に重要な Mo、 Crを添加した場合についての発明である。 しかしながら、 Mo、 Crは非常に高価な元素 であり、 本発明が目的とする汎用の安価なめっき鋼板を製造するにはコストがかかり すぎる鋼成分構成である。 また、 PCT/JP99/04385号では Mnが多量に添加された材料 を、 より有利に Dual Phase型の複合 鋼板とするために Mo添加をするわけである 力 Moを添加すると鋼板中のバンド状組織の厚みがより厚くなつてしまう。 このため、 プレス割れの起点になって、 逆に加工性が劣化してしまい、 このパンド状組織を解消 するために高温焼鈍が必要不可欠なものとなってしまう。 この高 ¾¾Π熱は 2回加熱法 のときはめつき性に有効に働くが、 1 回加熱法のときは逆に不利となってしまうので 必ずしも 2つのプロセスを両立する良い条件ではない。  PCT / JP99 / 04385 added Mo and Cr, which are very important for the production of a dual-phase composite-structured steel sheet having a low-temperature transformation phase with martensite as the main phase, on the ferrite matrix described above. It is an invention for the case. However, Mo and Cr are very expensive elements, and have a steel composition that is too costly to produce a general-purpose and inexpensive plated steel sheet as the object of the present invention. In PCT / JP99 / 04385, Mo is added to a material with a large amount of Mn to form a dual phase composite steel sheet more advantageously. Becomes thicker. For this reason, it becomes a starting point of press cracking, and conversely, the workability is deteriorated, and high-temperature annealing is indispensable to eliminate this band-like structure. This high heat is effective for the adhesiveness when using the double heating method, but it is disadvantageous when using the single heating method, so it is not necessarily a good condition to balance the two processes.
—方、 PCT/JP00/02547号は、 Mn ： 1. 0〜3. 0%、 Siを 0. 3〜： I. 8%添加した強度-伸 びバランスを向上させるのに非常に重要な残留オーステナイト相と焼戻しマルテンサ イト相を含む複合組織めつき鋼板である。 しかしながら、 これらの «得るには、 一 次の加熱冷却工程と、 二次の加熱冷却工程との組合せが必須である。 また、 一次の加 熱後の冷却過程では、 加熱後、 10°C/ s以上の冷却速度で一気に Ms点以下まで焼き入 れ処理を施す必要があり、 操業上かなり難しい問題がある。 また通常、 1回の加熱 - 冷却工程で済むはずの CGLラインの前で余分な加熱冷却工程を少なくとも 1回以上施 さなくてはならない。 発明の開示 On the other hand, PCT / JP00 / 02547 shows that Mn: 1.0-3.0%, Si 0.3-: I. 8% added, very important residue to improve strength-elongation balance This is a steel sheet with a composite structure containing an austenitic phase and a tempered martensite phase. However, in order to obtain these, a combination of a primary heating / cooling step and a secondary heating / cooling step is essential. Also, in the cooling process after the primary heating, it is necessary to quench at a stretch to a temperature below the Ms point at a cooling rate of 10 ° C / s or more after heating, which poses a problem in terms of operation. Also usually one heating- At least one extra heating / cooling step must be performed before the CGL line, which should have completed the cooling step. Disclosure of the invention
そこで、 本発明者らは、 従来技術が抱えている上記問題を解決するために、 連続溶 融亜鉛めっきラインなどの設備を用いて溶融亜鉛めつきしても、 良好な加工性と高強 度をともに満たし、 しかも良好なめっき性が得られる高強度溶融亜鉛めつき鋼板の製 造方法を提案することを目的とする。  In order to solve the above-mentioned problems of the prior art, the present inventors have developed good workability and high strength even when hot-dip galvanizing using equipment such as a continuous hot-dip galvanizing line. An object of the present invention is to propose a method for producing a high-strength hot-dip galvanized steel sheet that satisfies both requirements and that provides good plating properties.
本発明の具体的目的は、 加工性と高強度を表す指標として、 T S ： 590 MPa以上、 E 1 ： 25%以上、 T S X E 1の値： 15000 MPa · %以上を満たしつつ、 良好なめっき が得られることにある。  A specific object of the present invention is to obtain good plating while satisfying TS: 590 MPa or more, E1: 25% or more, and TSXE 1 value: 15000 MPa ·% or more as indices indicating workability and high strength. Is to be done.
今回、 発明者らは、 上記 の解決に向けて鋭意研究した結果、 Mo、 Crを添 せず とも、 また、 糸慮的に残留オーステナイト相と焼戻しマルテンサイト相を含まなくと も、 加工性およびめつき性に優れた高強度溶融亜鉛めつき鋼板および製造方法を知見 し、 本発明を完成するに至った。  The present inventors have conducted intensive studies for the above-mentioned solution, and as a result, have found that the workability and the workability are improved without adding Mo and Cr and without including the residual austenite phase and the tempered martensite phase. The present inventor has discovered a high-strength hot-dip galvanized steel sheet having excellent plating properties and a manufacturing method, and has completed the present invention.
すなわち、 本発明は、 以下の構成を要旨とするものである。  That is, the gist of the present invention is as follows.
(1)  (1)
C ： 0. 01〜0. 20wt%, Si ： 1. 0 wt%以下、  C: 0.01 to 0.20 wt%, Si: 1.0 wt% or less,
Mn： 1. 5超〜 3. 0 wt%、 P ： 0. 10wt%以下、  Mn: more than 1.5 to 3.0 wt%, P: 0.10 wt% or less,
S ： 0. 05wt%以下、 A1 ： 0. 10wt%以下、  S: 0.05 wt% or less, A1: 0.10 wt% or less,
N ： 0. 010 wt°/0以下を含み、 かつ N: contains 0.010 wt ° / 0 or less, and
Ti、 Nbおよび Vから選ばれるいずれか 1種または 2種以上を合計で、 0. 010 〜1. 0 wt%含有し、残部は Feおよび不可避的不純物の組成からなるとともに、フェライト相 の面積率が 50wt%以上、かつフェライト相の平均結晶粒径が 10 m以下であって、第 2相からなるパンド状組織の厚みが、 T b T≤ 0. 005 (ただし、 T b ：パンド状組 織の板厚方向平均厚み、 T :鋼板 の関係を満たす金属組織を有することを特徴 とする加工性およびめつき性に優れた高強度溶融亜鉛めつき鋼板。  One or more selected from Ti, Nb and V are contained in a total of 0.010 to 1.0 wt%, and the balance consists of the composition of Fe and unavoidable impurities and the area ratio of the ferrite phase. Is 50 wt% or more, the average grain size of the ferrite phase is 10 m or less, and the thickness of the band-like structure composed of the second phase is TbT≤0.005 (where Tb is the band-like structure). A high-strength hot-dip galvanized steel sheet having excellent workability and plating properties, characterized by having a metal structure satisfying the relationship of T: steel sheet in the thickness direction.
(2)  (2)
C ： 0. 01〜0. 20wt% Si ： 1. 0 wt%以下、 n： 1. 5超〜 3. 0 wt%、 P ： 0. 10 ％以下、 C: 0.01 to 0.20 wt% Si: 1.0 wt% or less, n: more than 1.5 to 3.0 wt%, P: 0.10% or less,
S ： 0.05wt%以下、 Al： 0. 10wt%以下、  S: 0.05 wt% or less, Al: 0.10 wt% or less,
N： 0. 010 wt%以下を含み、 かつ  N: Including 0.001 wt% or less, and
Ti、 Nbおよび Vから選ばれるいずれか 1種または 2種以上を合計で、 0. 010〜： 1. 0 wt%含み、 さらに Cuおよび Niのうちの 1種または 2種を合計で 3.0 wt%以下含有し、 残部は Fe および不可避的不純物の組成からなるとともに、 フェライト相の面積率が 50%以上、 かつフェライト相の平均結晶粒径が 10 m以下であって、 第 2相からなる バンド TO織の厚みが、 T b ZT≤0. 005 (ただし、 T b ：バンド状組織の板厚方向 平均厚み、 T :鋼板板厚） の関係を満たす金属組織を有することを特徴とする加工性 およびめつき性に優れた高強度溶融亜鈴めつき鋼板。  One or more selected from the group consisting of Ti, Nb, and V, in a total of 0.010 to: 1.0 wt%, and one or two of Cu and Ni in a total of 3.0 wt% And the balance consists of the composition of Fe and unavoidable impurities, the area ratio of the ferrite phase is 50% or more, the average crystal grain size of the ferrite phase is 10 m or less, and the band TO composed of the second phase Workability characterized by having a metal structure in which the weave thickness satisfies the relationship of TbZT≤0.005 (where Tb is the average thickness of the band-like structure in the thickness direction, and T is the thickness of the steel plate). High-strength molten dumbbell-plated steel sheet with excellent plating properties.
(3)  (3)
上記 （1)または （2)に記載の鋼組成からなるスラブを、熱間圧延して、 750〜450 °C で卷き取り、 次いで、 そのまま或いはさらに冷間圧延を行い、 得られた熱延板または 冷延板を、 750 °C以上に加熱し、 この温度からの冷却途中で溶融亜鈴めつきを行うこ とを特徴とする加工性およびめつき性に優れた高強度溶融亜鉛めつき鋼板の製造方法。 The slab having the steel composition described in the above (1) or (2) is hot-rolled and wound at 750 to 450 ° C, and then directly or further cold-rolled to obtain the obtained hot-rolled steel. High-strength hot-dip galvanized steel sheet with excellent workability and hot-dipability, characterized in that the hot-dip or cold-rolled sheet is heated to 750 ° C or more and the hot dipping is performed during cooling from this temperature. Manufacturing method.
(4) (Four)
上記 （1)または （2)に記載の鋼組成からなるスラブを、熱間圧延して、 750〜450 T で卷き取り、 次いで、 そのまま或いはさらに冷間圧延を行い、 得られた熱延板または 冷延板を、 750 °C以上に加熱し、 この温度からの冷却途中で溶融亜鉛めつきを行い、 次いで合金化処理を行うことを特徴とする加工性およびめつき性に優れた高強度溶融 亜鉛めつき鋼板の製造方法。  A slab having the steel composition described in (1) or (2) above is hot-rolled and wound at 750 to 450 T, and then directly or further cold-rolled to obtain a hot-rolled sheet. Or High strength with excellent workability and adhesion, characterized by heating a cold-rolled sheet to 750 ° C or more, performing hot-dip galvanizing during cooling from this temperature, and then performing alloying treatment. Manufacturing method for hot-dip galvanized steel sheet.
(5)  (Five)
上記 （1)または （2)に記載の鋼組成からなるスラブを、熱間圧延して、 750〜450 °C で卷き取り、 次いで、 そのまま或いはさらに冷間圧延を行レ、、 得られた熱延板または 冷延板を、 ー且 750 °C以上に加熱し冷却してから、 さらに 700 °C以上に加熱して、 こ の温度からの冷却途中で溶融亜鉛めつきを行うことを特徴とする加工性およびめつき 性に優れた高強度溶融亜鉛めつき鋼板の製造方法。  The slab having the steel composition described in the above (1) or (2) was hot-rolled and wound at 750 to 450 ° C, and then cold-rolled as it was or obtained. The hot or cold rolled sheet is heated to 750 ° C or higher and cooled, and then heated to 700 ° C or higher, and hot-dip zinc plating is performed during cooling from this temperature. A method for manufacturing a high-strength hot-dip galvanized steel sheet with excellent workability and plating properties.
(6)  (6)
上記 （1)または （2)に記載の鋼組成からなるスラブを、熱間圧延して、 750〜450 °C で卷き取り、 次いで、 そのまま或いはさらに冷間圧延を行い、 得られた熱延板または 冷延板を、 一旦 750 °C以上に加熱し冷却してから、 さらに 700 °C以上に加熱して、 こ の温度からの冷却途中で溶融亜鉛めつきを行い、 次いで合金ィ匕処理を行うことを特徴 とする加工性およびめつき性に優れた高強度溶融亜鉛めつき鋼板の製造方法。 The slab having the steel composition described in the above (1) or (2) is hot-rolled to 750 to 450 ° C. And then cold-rolled as it is or further, and the obtained hot-rolled or cold-rolled sheet is once heated to 750 ° C or more, cooled, and then further heated to 700 ° C or more. A method for producing a high-strength hot-dip galvanized steel sheet having excellent workability and hot-dip properties, wherein hot-dip galvanizing is performed during cooling from this temperature, and then alloying is performed.
すなわち、  That is,
(1) Ti、 Nbおよび Vから選ばれるいずれか 1種または 2種以上を積極的に添加し、 TiC、 NbC、 VCなどの炭化物などの結晶粒界移動のピン止め効果により、 フェラ イト （ひ） 結晶粒を 10 /z m以下に微細化しておくことができ、 加熱時、 フェラ イト +オーステナイト （α + γ ) 2相域中に生成、 成長する γ粒、 あるいはォー ステナイト （y ) 単相域での γ粒の粗大ィ匕を抑制する効果。 (1) One or two or more selected from Ti, Nb and V are positively added, and the ferrite (Hb) is formed by a pinning effect of grain boundary movement of carbides such as TiC, NbC and VC. ) Crystal grains can be refined to 10 / zm or less, and γ grains or austenite (y) single phase, which forms and grows in ferrite + austenite ( α + γ) two phase region when heated The effect of suppressing the coarse gamma of γ grains in the region.
(2) 加熱前から存在し、 C, Μηを多量に含有した第 2相からなるバンド状組織の厚み 力 T b /T≤0. 005 (ただし、 T b ：バンド状«の板厚方向平均厚み、 T : 鋼板板厚） の関係を満たすように分散させる加熱の効果。  (2) Thickness of the band-like structure consisting of the second phase containing a large amount of C and Μη, existing before heating Force Tb / T≤0.005 (where Tb is the band-like average in the thickness direction) Thickness, T: The effect of heating to disperse so as to satisfy the relationship of
以上の相乗効果によって、 Mo、 Crを添加せずとも、 また組織的に残留オーステナイ ト相と焼戻しマルテンサイト相を含まなくとも、 冷却前の γ粒が微細であるが故に冷 却中に起こる c相→γ相への（：、 の濃化を促進し、 有効に γ相をマルテンサイト化 し、 加工性およびめつき性に優れた高強度溶融亜鉛めつき鋼板が製造できることを見 出したのである。  Due to the synergistic effect described above, even if Mo and Cr are not added and the system does not contain residual austenite phase and tempered martensite phase, it occurs during cooling due to the fine γ grains before cooling.c It has been found that it is possible to produce a high-strength hot-dip galvanized steel sheet with excellent workability and adhesion by promoting the enrichment of (:,) into the phase → gamma phase, effectively transforming the gamma phase into martensite. is there.
とくに、 PCT/JP99/04385号および PCT/JP00/02547号のようにめつき性に有害な Cr、 Si を必須元素としてほとんど含まないので、 めっき性は極めて良好であり、 また Mo 添加がないので、 加熱前から存在するパンド状組織も比較的薄いので、 めっき性の観 点から不利な 1回 CGL法のときに高動 Π熱を施さなくても加工性の良好な高強度めつ き鋼板が製造できるというメリットがある。 図面の簡単な説明  In particular, since Cr and Si, which are harmful to plating, are scarcely contained as essential elements as in PCT / JP99 / 04385 and PCT / JP00 / 02547, the plating properties are extremely good, and there is no addition of Mo. However, since the band-like structure existing before heating is relatively thin, it is disadvantageous from the viewpoint of plating properties.High dynamics during the single CGL method. 高 High strength steel plate with good workability without heat. Has the merit that it can be manufactured. BRIEF DESCRIPTION OF THE FIGURES
図 1は、 引張強さ （T S )、 降伏強さ （Y S )、 伸び （E 1 ) 及びめつき性に及ぼす 連続溶融亜鉛めつきラインにおける加熱温度の影響を示すグラフである。  FIG. 1 is a graph showing the effect of the heating temperature in the continuous hot-dip galvanizing line on tensile strength (T S), yield strength (Y S), elongation (E 1), and plating properties.
図 2は、 引張強さ （T S )、 降伏強さ （Y S )、 伸び （E 1 ) 及びめつき性に及ぼす 卷取温度おょぴ 2回の加熱有無の影響を示すグラフである。 発明を実施するための最良の形態 FIG. 2 is a graph showing the effects of the application of two winding temperatures and the presence or absence of heating on the tensile strength (TS), yield strength (YS), elongation (E 1), and adhesion. BEST MODE FOR CARRYING OUT THE INVENTION
はじめに、 本発明の基になった実験結果について説明する。  First, experimental results based on the present invention will be described.
(実験 1 )  (Experiment 1)
化学組成が 0. 08wt% C—0. 01wt%Si-l. 9 wt%Mn-0. Oil wt% P—0.002 wt% S一 0. 04wt%Al-0. 0022wt%N-0. 02wt%Ti-0. 05wt%Nbで厚み 30mmのシートパ一を、 1200°Cに加熱し、 5パスで厚さ 2. 8 mmの熱延板とした。 その後、卷取り温度 (C T) 相当処理として 400°C， 650 °Cで各 l hrの熱処理を行った。 次いで、 酸洗後、 冷間圧 延して 1. 4 mmの冷延板とし、 700°C〜850 ^に 1分間加 ¾¾¾持し、 10でノ sの速度 で 500 まで冷却して、 溶融亜鉛めつき後、 40 s間保持後、 liTCZ sの速度で 550 まで加熱して合金化処理し、 ただちに liTCZ sの速度で室温まで冷却した。 その後、 圧下率 1. 0 %の調質圧延を行った。  Chemical composition 0.08wt% C-0.01wt% Si-l.9wt% Mn-0.Oil wt% P-0.002wt% S-0.04wt% Al-0.0022wt% N-0.02wt% A sheet paper having a thickness of 30 mm with Ti-0. 05 wt% Nb was heated to 1200 ° C to obtain a hot rolled sheet having a thickness of 2.8 mm in five passes. Thereafter, heat treatment was performed at 400 ° C and 650 ° C for each lhr as treatment corresponding to the winding temperature (C T). Then, after pickling, cold-rolled to a 1.4 mm cold-rolled plate, kept at 700 ° C to 850 ^ for 1 minute, cooled to 500 at a speed of 10 s at 10 and melted. After zinc plating and holding for 40 s, the alloy was heat-treated up to 550 at the rate of liTCZ s, and immediately cooled to room temperature at the rate of liTCZ s. After that, temper rolling was performed at a draft of 1.0%.
得られた溶融亜鉛めつき鋼板について、 J I S 5号引張試験片により引張特性 (T S、 Y S、 E l ) を調查するとともに、 めっき性を調べた。  With respect to the obtained hot-dip galvanized steel sheet, tensile properties (T S, Y S, El) were examined using a JIS No. 5 tensile test piece, and plating properties were examined.
めっき性は、 表面を目視で観察し、 次の基準で評価した。  The plating property was evaluated by observing the surface visually and according to the following criteria.
〇：不めっきなし （めっき性良好）  〇: No plating (good plating)
厶：不めっき一部発生 （めっき性やや良好）  ：： Partially unplated (Platability is slightly good)
X ：不めっき全面発生 （めっき性不良）  X: Non-plated entire surface (Plating poor)
得られた結果を図 1に示す。 図 1から、 卷取り温度が 650 °Cで、 めっき前の加熱温 度が 750 °C以上であるとき、 T S ： 590 MPa以上、 E 1 ： 25%以上を達成できること がわかる。  The results obtained are shown in FIG. Figure 1 shows that when the winding temperature is 650 ° C and the heating temperature before plating is 750 ° C or more, it is possible to achieve T S: 590 MPa or more and E 1: 25% or more.
(実験 2 )  (Experiment 2)
実験 1と同じ成分で C T相当処理を 400°C〜700 °Cに変化させた; KJ? 1. 6 mmの冷延 板を用い、 750 °Cに 1分間保持 （1回目加熱） を行い、 10で Z sの速度で室温まで冷 却して、 酸洗後、 750 °Cに 1分間保持 （2回目加熱） し、 10°CZ sの速度で 500°Cま で冷却して、 溶融亜鉛めつきし、 40 s間保持後、 lCTCZ sで 550°Cまで加熱して合金 化処理し、 ただちに lt cz sの速度で室温まで冷却した。 その後、 圧下率 1.0 %の調 質圧延を行った。  The CT equivalent treatment was changed from 400 ° C to 700 ° C with the same components as in Experiment 1; KJ? Using a 1.6 mm cold-rolled plate, holding at 750 ° C for 1 minute (first heating) After cooling to room temperature at a rate of Z s at 10 and pickling, keeping it at 750 ° C for 1 minute (second heating), cooling to 500 ° C at a rate of 10 ° C s, and adding molten zinc After plating and holding for 40 s, it was heated to 550 ° C. with lCTCZ s for alloying, and immediately cooled to room temperature at the rate of lt cz s. After that, temper rolling was performed at a rolling reduction of 1.0%.
得られた溶融亜鉛めつき鋼板について、 実験 1と同様にして、 引張特性とめっき性 を調べた。 その結杲、 2回の加熱 （1回目加熱と 2回目加熱） を行った場合 （図 2の 〇） には、 図 2に示すように、 引張特性、 めっき性ともに、 1回の加熱だけの実験 1 と同様の実験 （図 2の攀） の場合よりもさらに改善できることがわかる。 The tensile properties and plating properties of the obtained hot-dip galvanized steel sheet were determined in the same manner as in Experiment 1. Was examined. As a result, when two heatings (first heating and second heating) were performed (〇 in Fig. 2), as shown in Fig. 2, both the tensile properties and the plating properties were reduced by only one heating. It can be seen that the improvement can be made even more than in the experiment similar to Experiment 1 (the climb in Fig. 2).
上記各実験から、高 Mn含有量により高強度化した場合であっても、高温卷取り、 め つき前の高温加熱あるいは 2回の加熱処理により、 めつき性や機械特性が改善される ことがわかった。  From the above experiments, even when the strength is increased by the high Mn content, the hot-rolling, high-temperature heating before plating, or two heat treatments can improve the plating properties and mechanical properties. all right.
このような効果が得られる理由として、以下のようなことが考えられる。すなわち、 高温卷取り、 2回の加熱処理は、鋼板直下に、酸化し易い元素の内部酸化層を生成し、 これがめっき性に有害な Mnの鋼板表面への濃化を抑制すること、また、一度高^ J口熱 して生成しためっき性に有害な Mnの表面濃化層が、 2回目加熱の前に酸洗で除去され ること、 めっき前の高? ^ΛΠ熱は、 C、 Mn濃度の高いバンド組織を溶解 ·分散し、 マル テンサイトなどの第 2相の生成に有利に作用すること等が考えられる。  The following are conceivable reasons for obtaining such an effect. In other words, high-temperature winding and two heat treatments produce an internal oxide layer of an easily oxidizable element immediately below the steel sheet, which suppresses the concentration of Mn, which is harmful to plating properties, on the steel sheet surface. The high concentration of Mn, which is harmful to the plating property generated by high heat once, is removed by pickling before the second heating. High heat before plating? It is thought that it dissolves and disperses the band structure with a high concentration, and advantageously acts on the formation of the second phase such as martensite.
次に、 本発明において成分組成および製造条件を上記範囲に限定した理由について 説明する。 （成分組成は質量％で表す）  Next, the reasons for limiting the component composition and the production conditions to the above ranges in the present invention will be described. (Ingredient composition is expressed in mass%)
C ： 0. 01〜0. 20wt% C: 0.01 to 0.20 wt%
Cは鋼の重要な基本成分の一つであり、 とくに本発明では、 Ti、 Nbおよび Vの炭化 物を析出して強度上昇に寄与するほか、 低温で生成するべイナイト相、 マルテンサイ ト相を通じて強度の向上に寄与する元素である。 C量が、 0. 01wt%未満では、 上記析 出物はもちろん、 べィナイト相、 マルテンサイト相も生成しにくく、 一方、 0. 20wt% 超ではスポット溶接性が劣化することから、その含有範囲を 0. 01〜0. 20wt%とする。 なお、 好ましい C量は 0. 03〜0. 15wt%である。  C is one of the important basic components of steel.In the present invention, in particular, in the present invention, it precipitates carbides of Ti, Nb, and V and contributes to the increase in strength, as well as through the bainite and martensite phases formed at low temperatures. It is an element that contributes to improvement in strength. When the C content is less than 0.01 wt%, not only the above-mentioned precipitates but also the bainite phase and the martensite phase are hardly formed, while if it exceeds 0.20 wt%, the spot weldability deteriorates. To 0.01 to 0.20 wt%. The preferred C content is 0.03 to 0.15 wt%.
Si： 1. 0 wt%以下 Si: 1.0 wt% or less
Siは α相中の固溶 C量を減少させることにより、伸びなどの加工性を向上させる元 素であるが、 1. 0 wt%超の Si量の含有はスポット溶接性およびめつき性を損ねるので 上限を 1. 0 wt%とする。なお、好ましい Si量は 0. 5 wt%以下である。また、 0. 005wt% 未満に抑えるのはコストがかかるので下限を 0. 005wt%とするのが好ましい。  Si is an element that improves workability such as elongation by reducing the amount of solid solution C in the α phase.However, if the Si content exceeds 1.0 wt%, spot weldability and Since it is damaged, the upper limit is set to 1.0 wt%. The preferred amount of Si is 0.5 wt% or less. Further, it is costly to keep the content below 0.005 wt%, so the lower limit is preferably set to 0.005 wt%.
Mn： 1. 5超〜 3. 0 wt% Mn: more than 1.5 to 3.0 wt%
Mnは本発明における重要成分の一つであり、複合組織においては変態を抑制し、 Ί 相を安定化させる元素である。 し力 し、 1. 5 wt%以下の添加ではその効果がなく、 一 方、 3. 0 wt%超えるとスポット溶接性およびめつき性を著しく損なう。 よって、 MnはMn is one of the important components in the present invention, and is an element that suppresses transformation in a composite structure and stabilizes a liquid phase. However, the addition of 1.5 wt% or less has no effect. On the other hand, if it exceeds 3.0 wt%, the spot weldability and the plating property are significantly impaired. Therefore, Mn
1. 5超〜 3. 0 wt%、 好ましくは 1. 6 〜2. 5 wt%の範囲で添加する。 It is added in a range of more than 1.5 to 3.0 wt%, preferably 1.6 to 2.5 wt%.
P ： 0. 10wt%以下 P: 0.10 wt% or less
Pは高強度化を安価に達成するうえで有効な元素であるが、 0. 1 wt%を超えて含有 するとスポット溶接性を著しく損なうので上限を 0. 10wt%とする。 なお、 P量は 0. 05wt%以下に抑えるのが望ましレ、。また、 0. 001wt%未満に抑えるのはコストがかか るので下限を 0. 001wt%とするのが好ましい。  P is an effective element for achieving high strength at low cost, but if it exceeds 0.1 wt%, the spot weldability will be significantly impaired, so the upper limit should be 0.10 wt%. It is desirable to keep the P content to 0.05% by weight or less. In addition, since it is costly to keep the content below 0.001 wt%, the lower limit is preferably set to 0.001 wt%.
S ： 0. 05 ％以下  S: 0.05% or less
sは熱延時の熱間割れを引き起こす原因になるほか、 スポット溶接部のナゲット内 破断を誘発するので、極力低減するのが望ましレ、。よって、本発明では上限を 0. 05wt% 以下とする。 なお、 0. 010 wt%以下に抑制するのがより好ましい。 また、 0. 0005wt% 未満に抑えるのはコストがかかるので下限を 0. 0005wt%とするのが好ましい。  Since s causes hot cracking during hot rolling and also induces breakage in the nugget of the spot weld, it is desirable to reduce it as much as possible. Therefore, in the present invention, the upper limit is set to 0.05 wt% or less. It is more preferable to control the content to 0.010 wt% or less. In addition, since it is costly to suppress the content to less than 0.0005% by weight, the lower limit is preferably set to 0.0005% by weight.
A1： 0. 10wt%以下 A1: 0.1 wt% or less
A1は製鋼段階での脱酸剤として、また時効劣化を引き起こす Nを A1 Nとして固定す る有効な元素である。 しかし、 0· 10wt%超えて含有すると製造コストの上昇を招くの で、 A1量は 0. 1(^％以下に抑える必要がある。 なお、 好ましい含有量は 0. 050 wt% 以下である。 また、 0. 005wt%未満では十分に脱酸できないことから下限を 0. 005wt% とするのが好ましい。  A1 is an effective element as a deoxidizing agent at the steelmaking stage, and fixes N that causes aging deterioration as A1N. However, if the content exceeds 0.1 wt%, the production cost will increase, so the amount of A1 must be suppressed to 0.1 (^% or less. The preferable content is 0.005 wt% or less. If the content is less than 0.005% by weight, sufficient deoxidation cannot be achieved, so the lower limit is preferably set to 0.005% by weight.
N： 0. 010 wt%以下 N: 0.010 wt% or less
Nは時効劣化をもたらすほか、 降伏点 （降伏比） の上昇、 降伏伸びの発生を招くこ と力 ら、 0, 010 ％以下に抑制する必要がある。 なお、 好ましい N量は 0. 0050wt%以 下である。 また、 0. 0005wt°/o未満に抑えるのはコストがかかるので下限を 0. 0005wt% とするのが好ましい。  N must be suppressed to less than 0.010% because it causes aging deterioration, increases the yield point (yield ratio), and causes yield elongation. The preferred N content is 0.0005 wt% or less. In addition, since it is costly to suppress the content to less than 0.0005 wt ° / o, the lower limit is preferably set to 0.0005 wt%.
Ti、 Nbおよび V：合計で 0. 01〜1. 0 wt%  Ti, Nb and V: 0.01 to 1.0 wt% in total
Ti、 Nbおよび Vは炭化物を形成し、 鋼を高強度化するのに有効な元素であり、 1種 または 2種以上を合計で 0. 01〜； 1. 0 wt %を添加する。 これらの元素は合計量で 0. 0^^%以上の添加で上記効果が得られるが、 1. 0 wt%を超えて添加するとコスト上 の不利を招くほ力、 微細析出物が多くなりすぎて、 冷延後の回復 ·再結晶を抑制し、 延性 （伸び） を低下させる。 よって、 これらの元素は合計量で 0. 01〜1. 0 wt%、 好ま しくは 0. 010〜0. 20wt%の範囲で添加する。 Ti, Nb and V form carbides and are effective elements for increasing the strength of steel. One or more of them are added in a total amount of 0.01 to 1.0 wt%. The above effects can be obtained by adding these elements in a total amount of 0.0 ^^% or more.However, adding more than 1.0 wt% causes disadvantages in cost and excessively large amounts of fine precipitates. And suppresses recovery and recrystallization after cold rolling and reduces ductility (elongation). Therefore, these elements have a total amount of 0.01-1.0 wt%, preferably Alternatively, it is added in the range of 0.010 to 0.20 wt%.
Cu、 Ni：合計で 3. 0 wt%以下 Cu, Ni: 3.0 wt% or less in total
Cu、 Niはマルテンサイトなどの第 2相を形成し、鋼を高強度化するのに有用な元素 であり、 必要に応じて添加する。 しかしながら、 合計量で 3. 0 wt°/0を超えて添加する と、 コスト高となるだけでなく、 降伏点を低下させるので、 高降伏比が求められると きには不利となる。 このため、 Cu、 Niの含有量は合計で 3. 0 t%以下の範囲で添加す る。 なお、 好ましい含有範囲は、 合計量で 0. 010〜3. 0 wt%の範囲である。 また、 そ れぞれの元素を 0.005wt%未満に抑えるのはコストがかかるので下限をそれぞれ 0. 005wt°/oとするのが好ましい。 Cu and Ni are elements that form a second phase such as martensite and are useful for increasing the strength of steel, and are added as necessary. However, if the total amount exceeds 3.0 wt ° / 0 , it not only increases the cost but also lowers the yield point, which is disadvantageous when a high yield ratio is required. Therefore, the total content of Cu and Ni should be 3.0 t% or less. In addition, the preferable content range is a total amount of 0.010 to 3.0 wt%. In addition, since it is costly to suppress the content of each element to less than 0.005 wt%, it is preferable to set the lower limits to 0.005 wt ° / o.
Ca, REM： 0. 001〜0. 10wt%、 Ca, REM: 0.001 to 0.10 wt%,
Ca、 REM は、 介在物、 硫化物の形態を制御し、 穴拡げ性を改善するために、 0. 001wt% 以上添加することが好ましい。 しかしながら、 合計量で 0. 1 ^%を超えて添加すると、 コスト高となるとなる。 このため、じ3, 1?£¾1の含有量は0. 001〜0. 10 \^%以下の範囲で 添加することがこのましい。 なお、 さらに、 好ましい含有範囲は、 合計量で 0. 002〜 0. 05 wt%の範囲である。  Ca and REM are preferably added in an amount of 0.001% by weight or more in order to control the form of inclusions and sulfides and to improve hole expandability. However, adding more than 0.1 ^% in total would increase the cost. For this reason, it is preferable that the content of 3,1 to £ 1 is added in the range of 0.001 to 0.10%. Furthermore, a preferable content range is a range of 0.002 to 0.05 wt% in total amount.
フェライト相：面積率で 50wt%以上 Ferrite phase: 50 wt% or more in area ratio
本発明は高度な加工性が要求される自動車用鋼板を対象としており、 フェライト相 が面積率で 50 ％未満では必要な延性、伸びフランジ性を確保することが困難となる。 なお、 さらに良好な延性が要求される ^^は面積率で 75wt%以上のフェライト分率と することが望ましい。 フェライトとしては、 いわゆるフェライトのみでなく、 炭化物 の析出を含まないべィニティックフェライト、 ァシキユラ一フェライトも含むものと する。  The present invention is directed to a steel sheet for automobiles requiring high workability, and if the area ratio of the ferrite phase is less than 50%, it becomes difficult to secure necessary ductility and stretch flangeability. It should be noted that ^^, which requires even better ductility, is desirably a ferrite fraction of 75 wt% or more in area ratio. Ferrite shall include not only so-called ferrite but also vanitic ferrite which does not include precipitation of carbide, and ferrite.
フェライト相の観察方法および評価方法は、 鋼板の断面が観察面になるように樹脂 に埋め込み、 「純水 100m 1に対してピロ亜硫酸ナトリウム 1 g添加した水溶液」 と 「ェタノール 100m 1に対してピクリン酸 4 g添加した液」を 1： 1の割合で混合した 液中に室温で 1 2 0秒間浸漬してエッチングし、フェライト相（黒色部） と第 2相（白 色部） とに分離し、 倍率： X 1000の画像解析装置にて、 フェライトの面積率を求めた。 フェライト相の平均結晶粒径： 10 / m (0. 01謹)以下  The ferrite phase was observed and evaluated by embedding it in a resin so that the cross section of the steel plate was the observation surface, adding an aqueous solution containing 1 g of sodium pyrosulfite per 100 ml of pure water and a picrin solution for 100 ml of ethanol. The solution containing 4 g of acid ”was immersed in a solution mixed at a ratio of 1: 1 at room temperature for 120 seconds for etching to separate it into a ferrite phase (black area) and a second phase (white area). Magnification: The area ratio of ferrite was determined with an image analyzer of X1000. Average grain size of ferrite phase: 10 / m (0.01 min.) Or less
焼鈍で α + γの 2相域に加熱した際に、フェライト粒径が 10 μ πι超の大きさでは、 フェライト粒界から生成するオーステナイト粒は自ずと大きくなつてしまう。 当然、 この大きなオーステナイト粒は冷却中に比較的大きなマルテンサイトゃベーナイトな どの第 2相に変態し、 割れの起点となって穴拡げ性を低下させてしまう。 よって、 本 発明では、 第 2相を微細化し、 穴拡げ性の向上をはかるためにフェライト粒径を 10 /i m以下とした。 When heated to the α + γ two-phase region by annealing, if the ferrite grain size exceeds 10 μπι, Austenite grains formed from ferrite grain boundaries naturally become large. Naturally, these large austenite grains are transformed into a relatively large phase such as martensite-bainite during cooling, which serves as a starting point for cracking and reduces hole expandability. Therefore, in the present invention, the ferrite grain size is set to 10 / im or less in order to make the second phase finer and improve hole expandability.
ここで、 平均結晶粒径は断面組織写真から A S TMに規定された求積法により算出 した値と、 同じく切断法により求めた公称粒径 （例えば、 梅本ら：熱処理 24 (1984) 334 に解説あり） のより大きい方を採用する。 また、 本努明では第 2相の種類 （マル テンサイト、 ベーナイト、 パーライト、 セメンタイトなど） については特に限定する 必要がない。  Here, the average crystal grain size is the value calculated from the cross-sectional structure photograph by the quadrature method specified in ASTM and the nominal grain size similarly obtained by the cutting method (for example, Umemoto et al .: Heat treatment 24 (1984) 334 Yes), whichever is larger. In this effort, there is no need to specifically limit the type of phase 2 (martensite, bainite, perlite, cementite, etc.).
バンド状組織： T b /T≤0. 005 の厚み Banded structure: Tb / T≤0.005 thickness
バンド状組織は、 C，Mn量の多い鋼において、 主にスラブの冷却段階で結晶粒界に沿 つて凝集した C， Mnの濃化層が熱延時あるいはその後の冷延時に引き延ばされて圧延 方向、 板巾方向に列状、 層状になった第 2相群である。 これらバンド状 の平均厚 み T bと板厚 Tの比 T b /Tを 0. 005以下とする理由は、 本発明のように Mn含有量 が多い場合、熱延板の組織中に C、 Mriを主成分とするバンド状の第 2相組織が厚くな り、 フェライト素地中に硬質なマルテンサイトを均一に分散させた高強度鋼板を製造 しにくくなるからである。 よって、 効率よく高強度鋼板を製造するためには、 バンド 状の第 2相中に濃化している C、 Mnを分散しておく必要があり、 その目安となるのが バンド状組織の平均厚み T bと板厚 Tの比であり、 T b ZT≤0. 005 であれば良好な 結果が得られるからである。  The band-like structure of steel with a large amount of C and Mn is mainly due to the fact that the concentrated layer of C and Mn agglomerated along the grain boundaries during the cooling stage of the slab is elongated during hot rolling or subsequent cold rolling. This is a second phase group that is arranged in rows and layers in the rolling direction and the sheet width direction. The reason why the ratio Tb / T of the band-like average thickness Tb to the plate thickness T is 0.005 or less is that when the Mn content is large as in the present invention, C and C are contained in the structure of the hot-rolled sheet. This is because the band-shaped second phase structure mainly composed of Mri becomes thicker, and it becomes difficult to produce a high-strength steel sheet in which hard martensite is uniformly dispersed in a ferrite base. Therefore, in order to efficiently manufacture a high-strength steel sheet, it is necessary to disperse C and Mn concentrated in the band-like second phase, and the standard is the average thickness of the band-like structure. This is the ratio of Tb to plate thickness T, and good results can be obtained if TbZT≤0.005.
バンド状組織の厚み： Tbの観察方法および評価方法は、鋼板の断面が観察面になる ように樹脂に埋め込み、 3%ナイタール液中に室温で 15秒間浸漬してエッチングし、 倍率： X 1500の画像解析装置にて、 列状、 層状の第 2層組織を 20個測定し、 平均厚 み Tbを求めた。  Thickness of band-like structure: The observation method and evaluation method of Tb were as follows: embedded in resin so that the cross section of the steel plate became the observation surface, immersed in 3% nital solution at room temperature for 15 seconds, and etched. Using an image analyzer, 20 rows and 2 layers of the second layer tissue were measured, and the average thickness Tb was determined.
次に、 本発明における製造条件について述べる。  Next, the manufacturing conditions in the present invention will be described.
以上に述べた成分組成からなる鋼スラブを常法にしたがい熱間圧延し、 750〜450 °C で卷き取る。 卷取温度が 450 °C未満では、 Ti C， b Cなどの炭化物が生成しにくく、 強度不足になりやすく、 また、 鋼板の表面直下に内部酸化層を形成しにくく、 鋼板表 面での Mn濃化を抑制できなくなるからである。 一方、 750 °Cを超えて卷き取ると、 ス ケ一ル厚みが厚くなり酸洗効率が悪くなる他、 コイル長手方向の先端部、 中央部、 後 端部、 およびコイル幅方向のエッジ部、 中央部の間で材質変動が大きくなるからであ る。 なお、 好ましい卷取温度は 700 〜550 °Cである。 A steel slab having the above-described composition is hot-rolled in a conventional manner and wound at 750 to 450 ° C. If the winding temperature is less than 450 ° C, carbides such as TiC and bC are not easily generated, and the strength tends to be insufficient. Also, it is difficult to form an internal oxide layer directly under the surface of the steel sheet. This is because Mn concentration on the surface cannot be suppressed. On the other hand, if the coil is wound above 750 ° C, the scale thickness will increase and the pickling efficiency will deteriorate, and the tip, center, and rear ends of the coil in the longitudinal direction, and the edge in the coil width direction This is because the material variation between the central portions becomes large. The preferred winding temperature is 700 to 550 ° C.
この熱延板を必要により酸洗して脱スケールを行い、 熱延のまま、 或いはさらに冷 間圧延した後、 連続溶融亜鉛めつきラインにて 750 °C以上に加熱、 冷却し、 冷却途中 で溶融亜鉛めつきを行う。  The hot-rolled sheet is descaled by pickling as necessary, and then hot-rolled, or after further cold rolling, heated and cooled to 750 ° C or more in a continuous hot-dip galvanizing line. Perform hot-dip galvanizing.
また、 2回の加熱を行う場合には、 先ずはじめに連続焼鈍設備等で 750 °C以上に加熱 ( 1回目加熱）、 冷却したのち、 次に連続溶融亜鉛めつきラインにて 700 °C以上に加 熱 （2回目加熱）、 冷却し、 冷却途中、 好ましくは 420〜600°Cで溶融亜鉛めつきを行 う。 When heating twice, first heat to 750 ° C or more (continuous heating) using continuous annealing equipment, etc., then cool, and then to 700 ° C or more in the continuous molten zinc plating line. Heating (second heating), cooling, and hot-dip galvanizing, preferably at 420 to 600 ° C.
めっき前に、 ー且、 750 °C以上の温度域 （好ましくは、 750 〜900 °C) に加熱して 冷却することによって、バンド状糸 中に濃化している Mn等を分散させ、効率よくフ ェライト +マルテンサイトの複合 を形成させて、 加工性の向上をはかることが可 能になる。すなわち、本発明のように Mn含有量が多い場合、熱延板中にはバンド状の 第 2相組織が形成されやすく、 γ相中の Mn等の濃度が低下して複合組織形成に不利に なる。 そこで、 このパンド状組織の厚みを薄くし、 細かく分散させておけば、 連続溶 融亜鉛めっきラインのめっき過程、 あるいはさらに合金化処理過程などで 500 °C近傍 に保持された場合に、 γ相中の Mn等の濃化量が増すので、フェライト素地中にマルテ ンサイト相を好適に分散させることが可能になるのである。  Prior to plating, by heating to a temperature range of 750 ° C or more (preferably 750 to 900 ° C) and cooling, the Mn and the like concentrated in the band-like yarn are dispersed, and the efficiency is improved. Formability of ferrite + martensite can be formed to improve workability. That is, when the Mn content is high as in the present invention, a band-like second phase structure is easily formed in the hot-rolled sheet, and the concentration of Mn and the like in the γ phase is reduced, which is disadvantageous for forming a composite structure. Become. Therefore, if the thickness of the band-like structure is reduced and finely dispersed, the gamma phase will be reduced when it is kept at around 500 ° C during the plating process of the continuous galvanizing line or the alloying process. Since the enrichment amount of Mn and the like in the inside increases, it becomes possible to disperse the martensite phase in the ferrite base material suitably.
また、 2回の加熱を行う場合の 2回目加熱は 700 °C以上で行う。 2回目加熱は必然 的に連続溶融亜鉛めつきラインで行うことになる。 2回目加熱温度が 700 °Cに満たな いと、 連続溶融亜鉛めつきラインにおいて鋼板表面が還元されず、 めっき不良を生じ やすくなる。 この 2回目加熱温度は、 好ましくは 750〜800 °Cの範囲がよい。 なお、 2回の加熱を行う場合には、 1回目加熱で生成した Mn等の表面濃化層を除去し、その 後のめっき性を高めるために酸洗するのが望ましい。この酸洗条件としては、 30〜70°C で、 1〜10%HC 1水溶液中で 3〜10 s程度が好ましい。  In the case where heating is performed twice, the second heating is performed at 700 ° C or more. The second heating is inevitably performed in the continuous hot-dip galvanizing line. If the second heating temperature is less than 700 ° C, the surface of the steel sheet is not reduced in the continuous hot-dip galvanizing line, and plating defects are likely to occur. This second heating temperature is preferably in the range of 750 to 800 ° C. When heating is performed twice, it is preferable to remove the surface-concentrated layer of Mn and the like generated in the first heating and then to perform pickling in order to enhance plating properties thereafter. The pickling conditions are preferably about 30 to 70 ° C. and about 3 to 10 s in a 1 to 10% HCl aqueous solution.
以上の加熱工程を経てから、 溶融亜鉛めつきを行い、 場合によっては、 溶融亜鉛め つきを行った後、 引き続き合金化処理を行ってもよい。 実施例 1 After the above-described heating step, the molten zinc plating is performed. In some cases, the alloying treatment may be performed after the molten zinc plating is performed. Example 1
表 1に示す化学組成で、 厚さ 300 mmの連続铸造スラブを、 1200°Cに加熱し、 3パ スの ¾ΙΞ延後、 7スタンドの仕上げ圧延機で厚さ 2. 5 mmの熱延板として卷き取った。 その熱延板を酸洗後、 熱延板のまま、 または熱延板をさらに板厚 1. 2 mmに冷延後、 (1)連続焼鈍ラインでの 1回目加熱一酸洗一連続溶融亜鉛めつきラインでの 2回目力!] 熱、または （2)連続溶融亜鉛めつきラインでの加熱一亜鉛めつき、の工程でめっきし、 さらに一部分から採取したサンプルについては合金化処理した。 これらの製造条件を 表 2に示す。  A 300 mm thick continuous slab with the chemical composition shown in Table 1 was heated to 1200 ° C, rolled for 3 passes, and then rolled to a 2.5 mm thick hot rolled sheet with a 7-stand finishing mill. And wound it up. After pickling the hot-rolled sheet, leave the hot-rolled sheet as it is, or cold-roll the hot-rolled sheet further to a thickness of 1.2 mm. (1) First heating in a continuous annealing line Second plating in the plating line!] Heat, or (2) heating in the continuous hot-dip galvanizing line, plating in the step of zinc plating, and the sample taken from a part was alloyed. Table 2 shows the manufacturing conditions.
なお、加熱後の CGL条件としては、加熱〜めっきまでの鋼板の平均冷却速度を 10°C /sとし、 以下条件のめっき浴に浸漬した後、 ガスワイビングにより 60 g /m2の目付け 量に調整した。 その後、 490°Cまで加熱し、 20 s保持した後、 平均冷却速度を 20°C/s で 200°C以下まで冷却した。  CGL conditions after heating were as follows: the average cooling rate of the steel sheet from heating to plating was 10 ° C / s.After immersion in the plating bath under the following conditions, the basis weight was adjusted to 60 g / m2 by gas wiping. . Thereafter, the sample was heated to 490 ° C, held for 20 seconds, and then cooled at an average cooling rate of 20 ° C / s to 200 ° C or less.
•組成： 0. 15%A1-Zn  • Composition: 0.15% A1-Zn
•温度： 470°C  • Temperature: 470 ° C
•浸漬時間： 1 s  • Immersion time: 1 s
得られた鋼板を供 として、 機械的特性、 めっき性、 スポット溶接性などについ て調査した。 その結果を表 2に示す。  Using the obtained steel sheet as a sample, the mechanical properties, plating properties, spot weldability, etc. were investigated. The results are shown in Table 2.
ここで、 機械的特性、 めっき性、 合金化処理性、 スポット溶接性は以下の方法で評 価し 7こ。  Here, the mechanical properties, plating properties, alloying treatment properties, and spot weldability were evaluated by the following methods.
•機械的特性 （引張試験、 穴拡げ試験により調査）  • Mechanical properties (investigated by tensile test and hole expansion test)
鋼板より圧延直角方向に採取した J I S Z 2 2 0 4に規定の 5号試験片を用い、 J I S Z 2 2 4 1に規定の方法で降伏強さ （Y S )、 引張強さ （T S )、 破断伸び (E 1 )、 降伏伸び （Y E 1 ) を測定した。  Using a No. 5 test piece specified in JISZ224 and a test piece specified in JISZ2241, yield strength (YS), tensile strength (TS), elongation at break ( E 1) and yield elongation (YE 1) were measured.
伸ぴフランジ性を調べるため、 J F S T 1 0 0 1に規定の穴拡げ試験により、 穴拡げ率 （λ ) を測定した。  In order to examine the stretch flangeability, the hole expansion ratio (λ) was measured by a hole expansion test specified in JFST 1001.
•めっき性  • Plating property
良好：不めっき欠陥なし  Good: No non-plating defects
やや良好：不めっき欠陥一部発生  Slightly good: Some non-plating defects occurred
不良：不めっき欠陥多数発生 •合金化処理性 Bad: many non-plating defects • Alloying processability
良好：合金化ムラの全くないもの  Good: No alloying unevenness
やや良好：わずかに合金化ムラのあるもの  Slightly good: Slightly uneven alloying
不良：合金化ムラの著しいもの  Poor: one with significant alloying unevenness
•スポット溶接性  • Spot weldability
スポット溶接は、 welding electrode： ドーム型先端径 6ψ、 electrode force :3.10kN、 welding current- (kK, squeeze time :25cyc， setup time :3cyc， welding time:13cyc, holding time :25cycの溶接条件で行い、 J I S Z 3136の方法の引張剪断試験に よる引張荷重 （TSS) と、 J I S Z 3137 の方法の十字形引張試験による引張荷重 (CTS) を行い、 板厚 1. 2 mmの場合の基準引張剪断荷重である 8787N以上で、 かつ 延性比 (CTS/TSS) が 0.25以上のものを 「優」、 これらの値を満足しないものを 「劣」 として評価した。 Spot welding is performed under the welding conditions of welding electrode: dome-shaped tip diameter 6 mm, electrode force: 3.10 kN, welding current- (kK, squeeze time: 25 cyc, setup time: 3 cyc, welding time: 13 cyc, holding time: 25 cyc. Tensile load (TSS) by the tensile shear test according to the method of JISZ 3136 and tensile load (CTS) by the cross-shaped tensile test according to the method of JISZ 3137 are the standard tensile shear loads for a board thickness of 1.2 mm. Those with 8787N or more and a ductility ratio (CTS / TSS) of 0.25 or more were evaluated as “excellent”, and those that did not satisfy these values were evaluated as “poor”.
表 1， 表 2から、 発明例は、 TS ： 590〜690MPaレベルで、 E 1 ： 25wt%以上の引 張特性を有し、 TS XE 1の値： 15000 MPa it%¾上で TS XE 1バランスも良好 であり、 めっき性、 合金化処理性、 スポット溶接性についてもとくに問題がないこと がわかった。  According to Tables 1 and 2, the invention example shows that TS: at a level of 590 to 690 MPa, E1: has a tensile characteristic of 25 wt% or more, and the value of TSXE1: 15,000 MPa it% ¾, balance of TSXE1 Was also good, and it was found that there were no particular problems with the plating properties, alloying treatment properties, and spot weldability.
実施例 2  Example 2
表 3に示す化学組成で、 厚さ 300 mmの連続錄造スラブを、 1200°Cに加熱し、 3パ スの &ΙΞ延後、 7スタンドの仕上げ圧延機で厚さ 3.0 mmの熟延板として表 4に示す 温度で卷き取った。 酸洗後、 熱延板のまま、 または熱延板をさらに板厚 1.2 mmに冷 延後、 熱延板のまま、 または熱延板をさらに板厚 1.2 mmに冷延後、 （1)連続焼鈍ラ インでの 1回目加熱一酸洗一連続溶融亜鉛めつきラインでの 2回目加熱、 または （2) 連続溶融亜鉛めつきラインでの加熱一亜鉛めつき、 の工程でめっきし、 一部について はさらに合金化処理を行った。 これらの製造条件を表 4に示す。  A continuous production slab having a chemical composition shown in Table 3 and having a thickness of 300 mm was heated to 1200 ° C, and after 3 passes & rolling, a 7-stand finishing rolling mill was used to produce a 3.0 mm-thick rolled sheet. It was wound at the temperatures shown in Table 4. After pickling, hot rolled sheet or hot rolled sheet is further cold rolled to a thickness of 1.2 mm, hot rolled sheet or hot rolled sheet is further cold rolled to a 1.2 mm thickness, (1) Continuous First heating at annealing line, second pickling at pickling and continuous heating at continuous hot-dip galvanizing line, or (2) Heating at continuous hot-dip galvanizing line at first hot-dip galvanizing Was further alloyed. Table 4 shows these manufacturing conditions.
(1)連続焼鈍ラインでの 1回目加熱—酸洗一連続溶融亜鉛めつきラインでの 2回目加 熱、または （2)連続溶融亜鉛めつきラインでの加熱一亜鉛めつき、の工程でめっきし、 さらに一部分から採取したサンプルを合金化処理した。 これらの製造条件を表 4に示 す。  (1) The first heating in the continuous annealing line-the second heating in the pickling and continuous hot-dip galvanizing line, or (2) The heating and zinc-plating in the continuous hot-dip galvanizing line Then, a sample taken from a portion was alloyed. Table 4 shows these manufacturing conditions.
得られた鋼板を供^ "として、 機械的特性、 めっき性、 スポット溶接性などについ て同様にして調査した。 その結果を表 4に併せて示す。 The obtained steel sheet is used as a material to improve mechanical properties, plating properties, spot weldability, etc. And investigated in the same way. The results are shown in Table 4.
なお、加熱後の CGL条件としては、加熱〜めっきまでの鋼板の平均冷却速度を 10°C とし、 以下条件のめっき浴に浸漬した後、 ガスワイビングにより 60 g /m2の目付け 量に調整した。 その後、 490°Cまで加熱し、 20 s保持した後、 平均冷却速度を 20°C/s で 200°C以下まで冷却した。  As the CGL conditions after heating, the average cooling rate of the steel sheet from heating to plating was 10 ° C. After immersion in the plating bath under the following conditions, the basis weight was adjusted to 60 g / m2 by gas wiping. Thereafter, the sample was heated to 490 ° C, held for 20 seconds, and then cooled at an average cooling rate of 20 ° C / s to 200 ° C or less.
•組成： 0. 15%A1-Zn  • Composition: 0.15% A1-Zn
•温度： 470°C  • Temperature: 470 ° C
•浸漬時間： 1 s  • Immersion time: 1 s
目付量： 60 g /m2 Weight per unit area: 60 g / m2
その結果、 発明例は、 T S X E 1バランスが良好であり、 高強度であるにもかかわ らず、 めっき性、 合金化処理性、 スポット溶接性について何ら問題がないことがわか つ 7こ。  As a result, it can be seen that the invention examples have good TSXE1 balance and high strength, but have no problem in plating property, alloying treatment property, and spot weldability.
実施例 3 Example 3
表 5に示す化学組成で、 厚さ 300 mmの連続铸造スラブを、 1200°Cに加熱し、 3パ スの ¾]Ξ延後、 7スタンドの仕上げ圧延機で厚さ 3. 0 mmの熱延板として表 6に示す 温度で卷き取った。 酸洗後、 板厚 1. 2mmに冷延後、 連続焼鈍ラインでの 1回目加熱 一酸洗一連続溶融亜鉛めつきラインでの 2回目加熱の工程でめっきし、 さらに合金化 処理を行った。 これらの製造条件を表 6に示す。  A continuous production slab with a chemical composition shown in Table 5 and having a thickness of 300 mm was heated to 1200 ° C, rolled for 3 passes, and then heat-treated to a thickness of 3.0 mm with a 7-stand finishing mill. It was wound as a roll at the temperatures shown in Table 6. After pickling, cold-rolled to a thickness of 1.2 mm, first heating in a continuous annealing line, plating in a second heating step in a single pickling-continuous hot-dip galvanizing line, and further alloying . Table 6 shows these manufacturing conditions.
得られた鋼板を供^ "として、 機械的特性、 めっき性、 スポット溶接性などについ て同様にして調査した。 その結果を表 6に併せて示す。  The obtained steel sheet was used as a sample, and mechanical properties, plating properties, spot weldability, and the like were similarly examined. The results are shown in Table 6.
なお、加熱後の CGL条件としては、加熱〜めっきまでの鋼板の平均冷却速度を 10°C とし、 以下条件のめっき浴に浸漬した後、 ガスワイビングにより 60 g /m2の目付け 量に調整した。 その後、 490°Cまで加熱し、 20 s保持した後、 平均冷却速度を 20°C/s で 200°C以下まで冷却した。  As the CGL conditions after heating, the average cooling rate of the steel sheet from heating to plating was 10 ° C. After immersion in the plating bath under the following conditions, the basis weight was adjusted to 60 g / m2 by gas wiping. Thereafter, the sample was heated to 490 ° C, held for 20 seconds, and then cooled at an average cooling rate of 20 ° C / s to 200 ° C or less.
•組成： 0. 15%A1-Zn  • Composition: 0.15% A1-Zn
•温度： 470°C  • Temperature: 470 ° C
•浸漬時間： 1 s  • Immersion time: 1 s
目付量： 60 g /m2 Weight per unit area: 60 g / m2
その結果、 発明例は、 T S X E 1バランスが良好であり、 高強度であるにもかかわ らず、 めっき性、 合金化処理性、 スポット溶接性について何ら問題がないことがわ力 つた o 産業上の利用可能性 As a result, the invention example has a good balance of TSXE 1 and high strength. And no problem with plating, alloying, and spot weldability.o Industrial applicability
以上説明したように本発明によれば、 めっき性に何ら問題のない、 降伏比が低く、 As described above, according to the present invention, there is no problem in plating property, the yield ratio is low,
T S X E 1パランスが良好な高強度溶融亜鉛めつき鋼板 （高強度合金化溶融亜鉛めつ き鋼板を含む） を提供することが可能になる。 したがって、 この発明は、 自動車の軽 量化 ·低燃費化を可能とするので、 地球環境の改善にも大きく貢献する。 TSXE 1 It is possible to provide high-strength hot-dip galvanized steel sheets (including high-strength alloyed hot-dip galvanized steel sheets) with good balance. Therefore, the present invention makes it possible to reduce the weight and fuel consumption of automobiles, which greatly contributes to the improvement of the global environment.
表 1 table 1
鋼 C Si Mn P S Al N Ti Nb V 備考 Steel C Si Mn P S Al N Ti Nb V Remarks
A 0.075 0.01 2.4 0.007 0.003 0.05 0.0022 0.02 0.05 - 適用鋼A 0.075 0.01 2.4 0.007 0.003 0.05 0.0022 0.02 0.05-Applicable steel
B 0.101 0.02 2.3 0.009 0.002 0.01 0.0032 0.21 0.03 - 適用鋼B 0.101 0.02 2.3 0.009 0.002 0.01 0.0032 0.21 0.03-Applicable steel
C 0.056 0.02 2.2 0.012 0.001 0.05 0.0025 0.01 0.03 0.03 適用鋼C 0.056 0.02 2.2 0.012 0.001 0.05 0.0025 0.01 0.03 0.03 Applicable steel
D 0.068 0.01 1.6 0.011 0.001 0.07 0.0033 0.06 - - 適用鋼D 0.068 0.01 1.6 0.011 0.001 0.07 0.0033 0.06--Applicable steel
E 0.098 0.04 1.8 0.012 0.002 0.06 0.0026 - 0.07 - 適用鋼E 0.098 0.04 1.8 0.012 0.002 0.06 0.0026-0.07-Applicable steel
F 0.051 0.01 1.7 0.012 0.001 0.04 0.0031 0.01 - 0.05 適用鋼F 0.051 0.01 1.7 0.012 0.001 0.04 0.0031 0.01-0.05 Applicable steel
G 0.084 0.01 1.6 0.008 0.001 0.02 0.0026 0.06 0.02 0.03 適用鋼G 0.084 0.01 1.6 0.008 0.001 0.02 0.0026 0.06 0.02 0.03 Applicable steel
H 0.064 0.02 1.5 0.009 0.002 0.03 0.0025 0.02 0.04 - 適用鋼H 0.064 0.02 1.5 0.009 0.002 0.03 0.0025 0.02 0.04-Applicable steel
I 0.039 0.02 1.6 0.005 0.003 0.04 0.0021 0.05 0.05 適用鋼I 0.039 0.02 1.6 0.005 0.003 0.04 0.0021 0.05 0.05 Applicable steel
J 0.163 0.03 1.6 0.016 0.002 0.05 0.0029 0.09 0.03 0.02 J 0.163 0.03 1.6 0.016 0.002 0.05 0.0029 0.09 0.03 0.02
CP 適用鋼  CP applicable steel
K 0.022 0.01 2.6 0.008 0.002 0.04 0.0027 0.07 0.01 適用鋼 し 0.074 0.01 1.7 0.01 0.001 0.04 0.0028 比較鋼 K 0.022 0.01 2.6 0.008 0.002 0.04 0.0027 0.07 0.01 Applicable steel 0.074 0.01 1.7 0.01 0.001 0.04 0.0028 Comparative steel
M 0.007 0.02 1.8 0.009 0.002 0.04 0.0021 0.025 比較鋼M 0.007 0.02 1.8 0.009 0.002 0.04 0.0021 0.025 Comparative steel
N 0.082 0.02 0.7 0.026 0.002 0.03 0.0028 0.016 比較鋼N 0.082 0.02 0.7 0.026 0.002 0.03 0.0028 0.016 Comparative steel
0 0.095 0.05 1.7 0.113 0.004 0.06 0.0032 0.033 比較鋼 0 0.095 0.05 1.7 0.113 0.004 0.06 0.0032 0.033 Comparative steel
Figure imgf000019_0001
Figure imgf000019_0001
表 3 Table 3
鋼 c Si Mn P s Al N 丁 i Nb V Cu Ni Ca REM 備考 p 0.097 0.01 1.8 0.005 0.001 0.08 00033 0.02 0.06 o 0.5 0.3 o 0.01 適用鋼 Steel c Si Mn P s Al N D i Nb V Cu Ni Ca REM Remarks p 0.097 0.01 1.8 0.005 0.001 0.08 00033 0.02 0.06 o 0.5 0.3 o 0.01 Applicable steel
Q 0.075 0.02 1.9 0.008 0.001 0.04 00030 0.02 0.11 o 1.2 0.8 o o 滴用鋼Q 0.075 0.02 1.9 0.008 0.001 0.04 00030 0.02 0.11 o 1.2 0.8 o o Drop steel
R 0.056 0.09 2.5 0.009 0.001 0.05 0.0025 0.01 0.09 0 0.9 0 0.003 0 適用鋼R 0.056 0.09 2.5 0.009 0.001 0.05 0.0025 0.01 0.09 0 0.9 0 0.003 0 Applicable steel
S 0.062 0.05 1.6 0.007 0.001 0.06 0.0033 0.07 0.03 1.2 0.8 0 0 jia用鋼S 0.062 0.05 1.6 0.007 0.001 0.06 0.0033 0.07 0.03 1.2 0.8 0 0 Steel for jia
T 0.092 0.04 3.2 0.012 0.002 0.06 0.0026 0.05 0.09 0.02 0 0 0.002 0 比較鋼T 0.092 0.04 3.2 0.012 0.002 0.06 0.0026 0.05 0.09 0.02 0 0 0.002 0 Comparative steel
U 0.181 0.9 1.0 0.008 0.001 0.04 0.0031 0.01 0.11 0.02 0 0 0.003 0 週用鋼U 0.181 0.9 1.0 0.008 0.001 0.04 0.0031 0.01 0.11 0.02 0 0 0.003 0 Weekly steel
V 0.225 0.01 2.3 0.025 0.001 0.03 0.0028 0 0.02 0 0 0 0 0 比較鋼V 0.225 0.01 2.3 0.025 0.001 0.03 0.0028 0 0.02 0 0 0 0 0 Comparative steel
W 0.061 0.01 1.9 0.009 0.001 0.08 0.0033 0.15 0.04 0 0 0 0 0 jii用鋼W 0.061 0.01 1.9 0.009 0.001 0.08 0.0033 0.15 0.04 0 0 0 0 0 jii steel
00 X 0.081 0.01 1.9 0.008 0.001 0.04 0.0030 0.02 0.11 0 0.5 0 0 0 週用鋼 00 X 0.081 0.01 1.9 0.008 0.001 0.04 0.0030 0.02 0.11 0 0.5 0 0 0 Weekly steel
Y 0.044 0.01 2.6 0.018 0.001 0.05 0.0025 0.01 0.14 0 0.5 0 0 0 週用鋼 Y 0.044 0.01 2.6 0.018 0.001 0.05 0.0025 0.01 0.14 0 0.5 0 0 0 Weekly steel
Z 0.074 0.01 1.8 0.007 0.001 0.06 0.0033 0.07 0.03 0.5 0.3 0 0 適用鋼 Z 0.074 0.01 1.8 0.007 0.001 0.06 0.0033 0.07 0.03 0.5 0.3 0 0 Applicable steel
Figure imgf000021_0001
Figure imgf000021_0001
表 5 Table 5
鋼 C Si Mn P s Al N Ti Nb V Cu Ni Ca REM 備考 a 0.062 0.25 2.9 0.007 0.001 0.042 0.0074 0.128 0.066 0 0.05 0.02 0 0 適用鋼 b 0.071 0.03 2.7 0.009 0.001 0.035 0.0026 0.023 0.09 0 0.01 0.01 0 0.01 適用鋼 c 0.012 0.35 2.3 0.006 0.011 0.045 0.0032 0.105 0.06 0 0.02 0.02 0.003 0.02 適用鋼 d 0.122 0.05 3.3 0.007 0.001 0.026 0.0024 0.07 0.03 0.95 0.31 0 0 比較鋼 e 0.092 1.12 2.7 0.009 0.001 0.052 0.0056 0.05 0.09 0.02 0 0 0.002 0 比較鋼 f 0.205 0.02 2.7 0.007 0.001 0.042 0.0029 0.08 0.08 0.02 0 0 0.003 0 比較鋼 g 0.195 0.01 2.3 0.113 0.001 0.033 0.0028 0.02 0 0 0 0 0 比較鋼 h 0.084 0.03 2.8 0.011 0.052 0.012 0.0029 0.15 0.04 0 0 0 0 0 比較鋼 Steel C Si Mn Ps Al N Ti Nb V Cu Ni Ca REM Remarks a 0.062 0.25 2.9 0.007 0.001 0.042 0.0074 0.128 0.066 0 0.05 0.02 0 0 Applicable steel b 0.071 0.03 2.7 0.009 0.001 0.035 0.0026 0.023 0.09 0 0.01 0.01 0 0.01 Applicable steel c 0.012 0.35 2.3 0.006 0.011 0.045 0.0032 0.105 0.06 0 0.02 0.02 0.003 0.02 Applicable steel d 0.122 0.05 3.3 0.007 0.001 0.026 0.0024 0.07 0.03 0.95 0.31 0 0 Comparative steel e 0.092 1.12 2.7 0.009 0.001 0.052 0.0056 0.05 0.09 0.02 0 0 0.002 0 Comparative steel f 0.205 0.02 2.7 0.007 0.001 0.042 0.0029 0.08 0.08 0.02 0 0 0.003 0 Comparative steel g 0.195 0.01 2.3 0.113 0.001 0.033 0.0028 0.02 0 0 0 0 0 Comparative steel h 0.084 0.03 2.8 0.011 0.052 0.012 0.0029 0.15 0.04 0 0 0 0 0 Comparative steel
1 0.081 0.01 3.0 0.015 0.001 0.041 0.0067 0 0.3 0.15 0 0 比較鋼 ro i 0.077 0.02 2.7 0.018 0.001 0.033 0.0025 0.003 0.005 0 0.5 0 0 0 比較鋼 k 0.008 0.01 1.6 0.023 0.001 0.055 0.0033 0.07 0.03 0.5 0.3 0 0 比較鋼1 0.081 0.01 3.0 0.015 0.001 0.041 0.0067 0 0.3 0.15 0 0 Comparative steel ro i 0.077 0.02 2.7 0.018 0.001 0.033 0.0025 0.003 0.005 0 0.5 0 0 0 Comparative steel k 0.008 0.01 1.6 0.023 0.001 0.055 0.0033 0.07 0.03 0.5 0.3 0 0 Comparative steel
1 0.066 0.05 1.7 0.007 0.001 0.038 0.0069 0.028 0.071 0 1.9 1.2 0 0 比較鋼 m 0.063 0.02 2.9 0.008 0.001 0.036 0.0032 0.023 0.066 0 2.2 0.9 0 0.02 比較鋼 1 0.066 0.05 1.7 0.007 0.001 0.038 0.0069 0.028 0.071 0 1.9 1.2 0 0 Comparative steel m 0.063 0.02 2.9 0.008 0.001 0.036 0.0032 0.023 0.066 0 2.2 0.9 0 0.02 Comparative steel
表 6 Table 6
1回目 2回目 フ Iラ仆 平均  1st 2nd time I average
CT 冷延 加熱 加熱 粒 θ Tb/T YS TS EL YPI YR YSxEI 合金化 ス *·"ト  CT Cold rolling Heating Grain θ Tb / T YS TS EL YPI YR YSxEI Alloying
No. 鋼 。c 有無 tmiS. mix. 面積率 粒径 MPa MPa % X X Mpa めっき性 処理性 溶接性 備考 No. steel. c Presence or absence tmiS. mix. Area ratio Particle size MPa MPa% X X Mpa Plating property Processing property Weldability Remarks
。G °c % m % . G ° c% m%
49 a 700 有 850 750 65 1.9 0.004 596 993 17 0.0 60 16881 良好 良好 優 本発明例 49 a 700 Yes 850 750 65 1.9 0.004 596 993 17 0.0 60 16881 Good Good Excellent Example of the present invention
50 400 850 750 66 1.8 0.004 602 1022 16 0.0 59 16352 不良 不良 優 比較例50 400 850 750 66 1.8 0.004 602 1022 16 0.0 59 16352 Defective Defective Excellent Comparative example
51 b 700 850 750 59 1.8 0.004 618 983 18 0.0 63 17694 良好 良好 4 優 本発明例51 b 700 850 750 59 1.8 0.004 618 983 18 0.0 63 17694 Good Good 4 Excellent Example of the present invention
52 700 850 680 57 1.8 0.003 602 893 18 0.0 67 16074 不良 不良 45 優 比較例52 700 850 680 57 1.8 0.003 602 893 18 0.0 67 16074 Defective Defective 45 Excellent Comparative example
53 c 700 850 750 63 2.0 0.004 511 812 19 0.0 63 15428 良好 良好 38 優 本発明例53 c 700 850 750 63 2.0 0.004 511 812 19 0.0 63 15428 good good 38 excellent Example of the present invention
54 d 700 850 750 56 2.2 0.011 553 1020 12 0.0 54 12240 良好 良好 24 劣 比較例54 d 700 850 750 56 2.2 0.011 553 1020 12 0.0 54 12 240 Good Good 24 Poor Comparative example
55 β 700 850 750 56 2.1 0.005 458 668 16 0.0 69 10688 不良 不良 32 劣 比較例55 β 700 850 750 56 2.1 0.005 458 668 16 0.0 69 10 688 Defective Defective 32 Poor Comparative example
56 f 700 850 750 47 1.5 0.006 624 812 15 0.0 77 12180 良好 良好 14 劣 比較例56 f 700 850 750 47 1.5 0.006 624 812 15 0.0 77 12 180 Good Good 14 Poor Comparative example
Γ 57 S 700 850 750 63 1.5 0.003 701 932 15 0.0 75 13980 良好 良好 12 劣 比較例Γ 57 S 700 850 750 63 1.5 0.003 701 932 15 0.0 75 13980 Good Good 12 Poor Comparative example
58 h 700 n 850 750 64 2.4 0.003 735 1025 12 0.0 72 12300 良好 良好 10 劣 比較例58 h 700 n 850 750 64 2.4 0.003 735 1025 12 0.0 72 12 300 Good Good 10 Poor Comparative example
59 I 700 n 850 750 52 2.5 0.004 533 853 17 0.0 62 14501 良好 良好 42 劣 比較例59 I 700 n 850 750 52 2.5 0.004 533 853 17 0.0 62 14 501 Good Good 42 Poor Comparative example
60 700 700 750 61 2.3 0.003 480 987 15 0.0 49 14805 良好 良好 40 劣 比較例60 700 700 750 61 2.3 0.003 480 987 15 0.0 49 14805 Good Good 40 Poor Comparative example
61 k 700 850 750 99 18.0 0.001 322 381 38 0.0 85 14478 良好 良好 82 優 比較例61 k 700 850 750 99 18.0 0.001 322 381 38 0.0 85 14 478 Good Good 82 Excellent Comparative example
62 I 700 850 750 81 2.7 0.002 542 826 18 0.0 66 14868 不良 不良 35 優 比較例62 I 700 850 750 81 2.7 0.002 542 826 18 0.0 66 14 868 Defective Defective 35 Excellent Comparative example
63 m 700 850 750 78 2.4 0.003 689 996 15 0.0 69 14940 良好 良好 36 劣 比較例 63 m 700 850 750 78 2.4 0.003 689 996 15 0.0 69 14 940 Good Good 36 Poor Comparative example

Claims

to N c p s 請求の範囲 鋼中に、 0.01〜0.20 t%, to N cps Claimed range 0.01 to 0.20 t%,
1.0 wt%以下、  1.0 wt% or less,
1.5超〜 3· 0 wt%、  More than 1.5 to 3.0 wt%,
0.10wt%以下、  0.10wt% or less,
0.05wt%以下、  0.05wt% or less,
0.10wt%以下、  0.10wt% or less,
0.010 wt%以下  0.010 wt% or less
を含み、 かつ Including, and
Ti、 Nbおよび Vから選ばれるいずれか 1種または 2種以上を合計で、 0.010〜1.0 wt%含有し、残部は Feおよび不可避的不純物の組成からなるとともに、フェライト相 の面積率が 50%以上、かつフェライト相の平均結晶粒径が 10 m以下であって、第 2 相からなるバンド状糸道の厚みが、 TbZT≤0.005 (ただし、 Tb :バンド状組織 の板厚方向平均厚み、 T :鋼板板厚） の関係を満たす金属a^を有することを特徴と する加工性およびめつき性に優れた高強度溶融亜鈴めっき鋼板。  One or more selected from Ti, Nb, and V are contained in a total of 0.010 to 1.0 wt%, and the balance consists of Fe and inevitable impurities, and the area ratio of the ferrite phase is 50% or more. And the average grain size of the ferrite phase is 10 m or less, and the thickness of the band-like yarn path composed of the second phase is TbZT≤0.005 (where Tb is the average thickness of the band-like structure in the thickness direction, T: High-strength hot-dipped dumbbell-coated steel sheet with excellent workability and adhesion, characterized by having metal a ^ that satisfies the relationship of (steel sheet thickness).
2. 請求の範囲第 1項において、 鋼中に、 さらに Cuおよび Mのうちの 1種または 2種以上を合計で 3.0 wt%以下含有することを特徴とする加工性およびめつき性に優 れた高強度溶融亜鉛めつき鋼板。 2. Excellent in workability and adhesion, characterized in that in claim 1, steel contains one or more of Cu and M in total of 3.0 wt% or less in total. High strength hot-dip galvanized steel sheet.
3. 請求の範囲第 1〜 2項において、鋼中に、 さらに Caおよび REMのうちの 1種ま たは 2種以上を合計で 0.001〜0.010 wt%以下含有することを特徴とする加工性およ びめつき性に優れた高強度溶融亜鉛めつき鋼板。 3. Claims 1 and 2, characterized in that the steel further contains one or more of Ca and REM in a total of 0.001 to 0.010 wt% or less. High-strength hot-dip galvanized steel sheet with excellent shrinkability.
4. C： 0.01〜0.20wt%、 4. C: 0.01 ~ 0.20wt%,
Si： 1.0 wt%以下、 Si: 1.0 wt% or less,
n： 1.5超〜 3.0 wt%、  n: more than 1.5 to 3.0 wt%,
P ： 0.10wt%以下、 M： S N p s S ： 0. 05wt%以下、 P: 0.10wt% or less, M: SN ps S: 0.05 wt% or less,
Al： 0. 10wt°/o以下、 Al: 0.1wt ° / o or less,
N： 0. 010 wt%以下  N: 0.010 wt% or less
を含み、 かつ Including, and
Ti、 Nbおよび Vから選ばれるいずれか 1種または 2種以上を合計で、 0. 010 〜 1. 0 wt%含有し、残部は Feおよび不可避的不純物の組成からなるスラブを、熱間圧延して、 750 〜450 °Cで卷き取り、 次いで、 そのまま或いはさらに冷間圧延を行い、 得られた 熱延板または冷延板を、 750 °C以上に加熱し、 この温度からの冷却途中で溶融亜鉛め つきを行うことを特徴とする加工性およびめつき性に優れた高強度溶融亜鉛めつき鋼 板の製造方法。  A slab containing 0.010 to 1.0 wt% in total of one or more selected from Ti, Nb and V, and the balance being Fe and unavoidable impurities, is hot-rolled. And then rolled as it is or further cold-rolled, and the obtained hot rolled or cold rolled sheet is heated to 750 ° C or more, and while cooling from this temperature, A process for producing a high-strength hot-dip galvanized steel sheet having excellent workability and hot-dipability, characterized by hot-dip galvanizing.
5 . 請求の範囲第 4項において、 スラブは、 さらに Cuおよび Niのうちの 1種また は 2種を合計で 3. 0 wt%以下含有することを特徴とする加工性およびめつき性に優れ た高強度溶融亜鉛めつき鋼板の製造方法。 5. The slab according to claim 4, wherein the slab further contains one or two of Cu and Ni in a total amount of 3.0 wt% or less, and is excellent in workability and adhesion. Method of manufacturing high-strength hot-dip galvanized steel sheet.
6 . 請求の範囲第 4 ~ 5項において、スラブは、 さらに Caおよび REMのうちの 1種 または 2種以上を合計で 0. 001〜0· 10 wt%以下含有することを特徴とする加工性およ びめつき性に優れた高強度溶融亜鉛めつき鋼板の製造方法。 6. The workability according to claims 4 to 5, wherein the slab further contains one or more of Ca and REM in a total of 0.001 to 0.10 wt% or less. A method for producing a high-strength hot-dip galvanized steel sheet with excellent plating properties.
7 . 請求の範囲第 4〜6項において、 さらに合金化処理を行うことを特徴とする加 ェ性およびめつき性に優れた高強度溶融亜鉛めつき鋼板の製造方法。 7. The method for producing a high-strength hot-dip galvanized steel sheet according to claim 4 or claim 6, further comprising an alloying treatment.
8 . C： 0. 01〜0. 20wt%、 8. C: 0.01-1.20 wt%,
1. 0 wt%以下、  1.0 wt% or less,
1. 5超〜 3. 0 wt%、  More than 1.5 to 3.0 wt%,
0. 10wt%以下、  0.1% by weight or less,
0. 05wt%以下、  0.05 wt% or less,
0. 10wt%以下、  0.1% by weight or less,
0. 010 wt%以下 を含み、 かつ 0.010 wt% or less Including, and
Ti、 Nbおよび Vから選ばれるいずれか 1種または 2種以上を合計で、 0. 010〜； 1. 0 wt%含有し、残部は Feおよび不可避的不純物の組成からなるスラブを熱間圧延して、 得られた熱延板を 750〜450 °Cで卷き取り、 次いで、 そのまま或いはさらに冷間圧延 を行い、 得られた熱延板または冷延板を、 一旦 750 °C以上に加熱し、 冷却してから、 さらに 700 °C以上に加熱して、 この温度からの冷却途中で溶融亜鉛めつきを行うこと を特徴とする加工性およびめつき性に優れた高強度溶融亜鉛めつき鋼板の製造方法。  One or two or more selected from Ti, Nb and V are contained in a total amount of 0.010 to 1.0% by weight, and the remainder is hot-rolled to a slab having a composition of Fe and unavoidable impurities. Then, the obtained hot rolled sheet is wound up at 750 to 450 ° C, and then cold rolled as it is or further, and the obtained hot rolled sheet or cold rolled sheet is once heated to 750 ° C or more. High-strength hot-dip galvanized steel sheet with excellent workability and plating properties, characterized in that after cooling, it is further heated to 700 ° C or more and hot-dip zinc plating is performed during cooling from this temperature. Manufacturing method.
9 . 請求の範囲第 8項において、 スラブは、 さらに Cuおよび Niのうちの 1種また は 2種を合計で 3. 0 wt%以下含有することを特徴とする加工性およびめつき性に優れ た高強度溶融 »めっき鋼板の製造方法。 9. The slab according to claim 8, wherein the slab further contains one or two of Cu and Ni in a total amount of 3.0 wt% or less, and is excellent in workability and adhesion. High-strength hot-dip »Method of manufacturing plated steel sheet.
10. 請求の範囲第 8〜 9項において、スラブは、 さらに Caおよび REMのうちの 1種 または 2種以上を合計で 0. 001〜0. 10 wt%以下含有することを特徴とする加工性およ びめつき性に優れた高強度溶融亜鉛めつき鋼板の製造方法。 10. The workability according to claims 8 to 9, wherein the slab further contains one or more of Ca and REM in a total of 0.001 to 0.10 wt% or less. A method for producing a high-strength hot-dip galvanized steel sheet with excellent plating properties.
11. 請求の範囲第 9〜10項において、 更に、 合金化処理を行うことを特徴とする加 ェ性およぴめっき性に優れた高強度溶融亜鉛めつき鋼板の製造方法。 11. The method for producing a high-strength hot-dip galvanized steel sheet according to claims 9 to 10, further comprising an alloying treatment, the steel sheet having excellent additivity and plating property.
PCT/JP2000/007115 1999-10-22 2000-10-13 Hot-dip galvanized steel sheet having high strength and also being excellent in formability and galvanizing property WO2001031077A1 (en)

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CA002353492A CA2353492C (en) 1999-10-22 2000-10-13 Hot-dip galvanized high-strength steel sheet having superior workability and galvanizability and method for producing the same
US09/868,674 US6537394B1 (en) 1999-10-22 2000-10-13 Method for producing hot-dip galvanized steel sheet having high strength and also being excellent in formability and galvanizing property
DE60033498T DE60033498T2 (en) 1999-10-22 2000-10-13 HOT-DIPPED GALVANIZED STEEL PLATE WITH HIGH STRENGTH AND EXCELLENT CHARACTERISTICS IN FORMING AND GALVANIZING
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